diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 000000000..58317d305 --- /dev/null +++ b/.gitattributes @@ -0,0 +1 @@ +cpp/* linguist-vendored diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 index 000000000..82459e469 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,47 @@ +Tantivy 0.3 +========================== + + +Special thanks to @Kodraus @lnicola @Ameobea @manuel-woelker @celaus +for their contribution to this release. + +Thanks also to everyone in tantivy gitter chat +for their advise and company :) + +https://gitter.im/tantivy-search/tantivy + + +Warning: + +Tantivy 0.3 is NOT backward compatible with tantivy 0.2 +code and index format. +You should not expect backward compatibility before +tantivy 1.0. + + +New Features +------------ + +- Delete. You can now delete documents from an index. +- Support for windows (Thanks to @lnicola) + + +Various Bugfixes & small improvements +---------------------------------------- + +- Added CI for Windows (https://ci.appveyor.com/project/fulmicoton/tantivy) +Thanks to @KodrAus ! (#108) +- Various dependy version update (Thanks to @Ameobea) #76 +- Fixed several race conditions in `Index.wait_merge_threads` +- Fixed #72. Mmap were never released. +- Fixed #80. Fast field used to take an amplitude of 32 bits after a merge. (Ouch!) +- Fixed #92. u32 are now encoded using big endian in the fst + in order to make there enumeration consistent with + the natural ordering. +- Building binary targets for tantivy-cli (Thanks to @KodrAus) +- Misc invisible bug fixes, and code cleanup. +- Use + + + + diff --git a/Cargo.toml b/Cargo.toml index 3e17a4cfc..7adb1fa47 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -1,6 +1,6 @@ [package] name = "tantivy" -version = "0.2.0" +version = "0.3.0" authors = ["Paul Masurel "] build = "build.rs" license = "MIT" @@ -29,14 +29,21 @@ libc = {version = "0.2.20", optional=true} num_cpus = "1.2" itertools = "0.5.9" lz4 = "1.20" +bit-set = "0.4.0" time = "0.1" uuid = { version = "0.4", features = ["v4", "rustc-serialize"] } chan = "0.1" version = "2" crossbeam = "0.2" +futures = "0.1.9" +futures-cpupool = "0.1.2" + +[target.'cfg(windows)'.dependencies] +winapi = "0.2" [dev-dependencies] rand = "0.3" +env_logger = "0.4" [build-dependencies] gcc = {version = "0.3", optional=true} diff --git a/README.md b/README.md index a58345a4b..2fcbe7a1c 100644 --- a/README.md +++ b/README.md @@ -1,9 +1,10 @@ ![Tantivy](https://tantivy-search.github.io/logo/tantivy-logo.png) [![Build Status](https://travis-ci.org/tantivy-search/tantivy.svg?branch=master)](https://travis-ci.org/tantivy-search/tantivy) -[![Coverage Status](https://coveralls.io/repos/github/tantivy-search/tantivy/badge.svg?branch=master)](https://coveralls.io/github/tantivy-search/tantivy?branch=master) -[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT) +[![Coverage Status](https://coveralls.io/repos/github/tantivy-search/tantivy/badge.svg?branch=master&refresh1)](https://coveralls.io/github/tantivy-search/tantivy?branch=master) [![Join the chat at https://gitter.im/tantivy-search/tantivy](https://badges.gitter.im/tantivy-search/tantivy.svg)](https://gitter.im/tantivy-search/tantivy?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) +[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT) +[![Build status](https://ci.appveyor.com/api/projects/status/r7nb13kj23u8m9pj?svg=true)](https://ci.appveyor.com/project/fulmicoton/tantivy) ![beacon for google analytics](https://ga-beacon.appspot.com/UA-88834340-1/tantivy/README) **Tantivy** is a **full text search engine library** written in rust. @@ -25,14 +26,17 @@ It is strongly inspired by Lucene's design. - LZ4 compressed document store - Cheesy logo with a horse -Tantivy supports Linux and MacOS. Windows is not supported. +Tantivy supports Linux, MacOS and Windows. + # Getting started - [tantivy's usage example](http://fulmicoton.com/tantivy-examples/simple_search.html) - [tantivy-cli and its tutorial](https://github.com/tantivy-search/tantivy-cli). It will walk you through getting a wikipedia search engine up and running in a few minutes. -- [reference doc](https://tantivy-search.github.io/tantivy/tantivy/schema/index.html). +- [reference doc] + - [For the last released version](https://docs.rs/tantivy/) + - [For the last master branch](https://tantivy-search.github.io/tantivy/tantivy/index.html) # Compiling diff --git a/appveyor.yml b/appveyor.yml new file mode 100644 index 000000000..789e24400 --- /dev/null +++ b/appveyor.yml @@ -0,0 +1,24 @@ +# Appveyor configuration template for Rust using rustup for Rust installation +# https://github.com/starkat99/appveyor-rust + +os: Visual Studio 2015 +environment: + matrix: + - channel: nightly + target: x86_64-pc-windows-msvc + - channel: nightly + target: x86_64-pc-windows-gnu + msys_bits: 64 + +install: + - appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe + - rustup-init -yv --default-toolchain %channel% --default-host %target% + - set PATH=%PATH%;%USERPROFILE%\.cargo\bin + - if defined msys_bits set PATH=%PATH%;C:\msys64\mingw%msys_bits%\bin + - rustc -vV + - cargo -vV + +build: false + +test_script: + - REM SET RUST_LOG=tantivy,test & cargo test --verbose \ No newline at end of file diff --git a/build.rs b/build.rs index ceba328cb..639bbe93f 100644 --- a/build.rs +++ b/build.rs @@ -1,40 +1,50 @@ -#[cfg(feature= "simdcompression")] +#[cfg(feature = "simdcompression")] mod build { extern crate gcc; - use std::process::Command; - pub fn build() { - Command::new("make") - .current_dir("cpp/simdcomp") - .output() - .unwrap_or_else(|e| { panic!("Failed to make simdcomp: {}", e) }); - gcc::Config::new() - .cpp(true) - .flag("-std=c++11") - .flag("-O3") - .flag("-mssse3") - .include("./cpp/simdcomp/include") - .object("cpp/simdcomp/avxbitpacking.o") - .object("cpp/simdcomp/simdintegratedbitpacking.o") - .object("cpp/simdcomp/simdbitpacking.o") - .object("cpp/simdcomp/simdpackedsearch.o") - .object("cpp/simdcomp/simdcomputil.o") - .object("cpp/simdcomp/simdpackedselect.o") - .object("cpp/simdcomp/simdfor.o") - .file("cpp/simdcomp_wrapper.cpp") - .compile("libsimdcomp.a"); - println!("cargo:rustc-flags=-l dylib=stdc++"); + let mut config = gcc::Config::new(); + config.include("./cpp/simdcomp/include") + .file("cpp/simdcomp/src/avxbitpacking.c") + .file("cpp/simdcomp/src/simdintegratedbitpacking.c") + .file("cpp/simdcomp/src/simdbitpacking.c") + .file("cpp/simdcomp/src/simdpackedsearch.c") + .file("cpp/simdcomp/src/simdcomputil.c") + .file("cpp/simdcomp/src/simdpackedselect.c") + .file("cpp/simdcomp/src/simdfor.c") + .file("cpp/simdcomp_wrapper.c"); + + if !cfg!(debug_assertions) { + config.opt_level(3); + + if cfg!(target_env = "msvc") { + config.define("NDEBUG", None) + .flag("/Gm-") + .flag("/GS-") + .flag("/Gy") + .flag("/Oi") + .flag("/GL"); + } else { + config.flag("-msse4.1") + .flag("-march=native"); + } + } + + config.compile("libsimdcomp.a"); + + // Workaround for linking static libraries built with /GL + // https://github.com/rust-lang/rust/issues/26003 + if !cfg!(debug_assertions) && cfg!(target_env = "msvc") { + println!("cargo:rustc-link-lib=dylib=simdcomp"); + } } } -#[cfg(not(feature= "simdcompression"))] +#[cfg(not(feature = "simdcompression"))] mod build { - pub fn build() { - } + pub fn build() {} } - fn main() { build::build(); } diff --git a/cpp/simdcomp_wrapper.c b/cpp/simdcomp_wrapper.c new file mode 100644 index 000000000..4530e3f3b --- /dev/null +++ b/cpp/simdcomp_wrapper.c @@ -0,0 +1,42 @@ +#include "simdcomp.h" +#include "simdcomputil.h" + +// assumes datain has a size of 128 uint32 +// and that buffer is large enough to host the data. +size_t compress_sorted( + const uint32_t* datain, + uint8_t* output, + const uint32_t offset) { + const uint32_t b = simdmaxbitsd1(offset, datain); + *output++ = b; + simdpackwithoutmaskd1(offset, datain, (__m128i *) output, b); + return 1 + b * sizeof(__m128i); +} + +// assumes datain has a size of 128 uint32 +// and that buffer is large enough to host the data. +size_t uncompress_sorted( + const uint8_t* compressed_data, + uint32_t* output, + uint32_t offset) { + const uint32_t b = *compressed_data++; + simdunpackd1(offset, (__m128i *)compressed_data, output, b); + return 1 + b * sizeof(__m128i); +} + +size_t compress_unsorted( + const uint32_t* datain, + uint8_t* output) { + const uint32_t b = maxbits(datain); + *output++ = b; + simdpackwithoutmask(datain, (__m128i *) output, b); + return 1 + b * sizeof(__m128i); +} + +size_t uncompress_unsorted( + const uint8_t* compressed_data, + uint32_t* output) { + const uint32_t b = *compressed_data++; + simdunpack((__m128i *)compressed_data, output, b); + return 1 + b * sizeof(__m128i); +} diff --git a/cpp/simdcomp_wrapper.cpp b/cpp/simdcomp_wrapper.cpp deleted file mode 100644 index bfcaf72ef..000000000 --- a/cpp/simdcomp_wrapper.cpp +++ /dev/null @@ -1,48 +0,0 @@ -#include -#include -#include -#include "simdcomp.h" -#include "simdcomputil.h" - -extern "C" { - - // assumes datain has a size of 128 uint32 - // and that buffer is large enough to host the data. - size_t compress_sorted_cpp( - const uint32_t* datain, - uint8_t* output, - const uint32_t offset) { - const uint32_t b = simdmaxbitsd1(offset, datain); - *output++ = b; - simdpackwithoutmaskd1(offset, datain, (__m128i *) output, b); - return 1 + b * sizeof(__m128i);; - } - - // assumes datain has a size of 128 uint32 - // and that buffer is large enough to host the data. - size_t uncompress_sorted_cpp( - const uint8_t* compressed_data, - uint32_t* output, - uint32_t offset) { - const uint32_t b = *compressed_data++; - simdunpackd1(offset, (__m128i *)compressed_data, output, b); - return 1 + b * sizeof(__m128i); - } - - size_t compress_unsorted_cpp( - const uint32_t* datain, - uint8_t* output) { - const uint32_t b = maxbits(datain); - *output++ = b; - simdpackwithoutmask(datain, (__m128i *) output, b); - return 1 + b * sizeof(__m128i);; - } - - size_t uncompress_unsorted_cpp( - const uint8_t* compressed_data, - uint32_t* output) { - const uint32_t b = *compressed_data++; - simdunpack((__m128i *)compressed_data, output, b); - return 1 + b * sizeof(__m128i); - } -} \ No newline at end of file diff --git a/examples/html/simple_search.html b/examples/html/simple_search.html index 1cfc7ac6e..1aa6b63ab 100644 --- a/examples/html/simple_search.html +++ b/examples/html/simple_search.html @@ -52,7 +52,7 @@
-

Let’s create a temporary directory for the +

Let’s create a temporary directory for the sake of this example

@@ -60,7 +60,7 @@ sake of this example

    if let Ok(dir) = TempDir::new("tantivy_example_dir") {
         run_example(dir.path()).unwrap();
         dir.close().unwrap();
-    }   
+    }
 }
 
 
@@ -78,7 +78,7 @@ sake of this example

               
Defining the schema

 
The Tantivy index requires a very strict schema.
 The schema declares which fields are in the index,
-and for each field, its type and “the way it should 
+and for each field, its type and “the way it should
 be indexed”.
@@ -111,12 +111,12 @@ be indexed”.

We want full-text search for it, and we want to be able to retrieve the document after the search.

TEXT | STORED is some syntactic sugar to describe -that.

+that.

TEXT means the field should be tokenized and indexed, along with its term frequency and term positions.

STORED means that the field will also be saved in a compressed, row-oriented key-value store. -This store is useful to reconstruct the +This store is useful to reconstruct the documents that were selected during the search phase.

@@ -139,7 +139,7 @@ to retrieve the body after the search.

    schema_builder.add_text_field("body", TEXT);
-    
+
     let schema = schema_builder.build();
@@ -173,14 +173,12 @@ with our schema in the directory.

There must be only one writer at a time. This single IndexWriter is already multithreaded.

-

Here we use a buffer of 1 GB. Using a bigger -heap for the indexer can increase its throughput. -This buffer will be split between the indexing -threads.

+

Here we use a buffer of 50MB per thread. Using a bigger +heap for the indexer can increase its throughput.

- 
    let mut index_writer = try!(index.writer(1_000_000_000));
+ 
    let mut index_writer = try!(index.writer(50_000_000));
@@ -213,10 +211,12 @@ one by one in a Document object.

    let title = schema.get_field("title").unwrap();
     let body = schema.get_field("body").unwrap();
-     
+
     let mut old_man_doc = Document::default();
     old_man_doc.add_text(title, "The Old Man and the Sea");
-    old_man_doc.add_text(body, "He was an old man who fished alone in a skiff in the Gulf Stream and he had gone eighty-four days now without taking a fish.");
+ old_man_doc.add_text(body, + "He was an old man who fished alone in a skiff in the Gulf Stream and \ + he had gone eighty-four days now without taking a fish."); @@ -231,7 +231,7 @@ one by one in a Document object.

- 
    try!(index_writer.add_document(old_man_doc));
+ 
    index_writer.add_document(old_man_doc);
@@ -248,13 +248,13 @@ a document object directly from json.

- 
    
+            
     let mice_and_men_doc = try!(schema.parse_document(r#"{
        "title": "Of Mice and Men",
        "body": "few miles south of Soledad, the Salinas River drops in close to the hillside bank and runs deep and green. The water is warm too, for it has slipped twinkling over the yellow sands in the sunlight before reaching the narrow pool. On one side of the river the golden foothill slopes curve up to the strong and rocky Gabilan Mountains, but on the valley side the water is lined with trees—willows fresh and green with every spring, carrying in their lower leaf junctures the debris of the winter’s flooding; and sycamores with mottled, white,recumbent limbs and branches that arch over the pool"  
     }"#));
-    
-    try!(index_writer.add_document(mice_and_men_doc));

+
+    index_writer.add_document(mice_and_men_doc);
@@ -275,7 +275,7 @@ The following document has two titles.

"title": ["Frankenstein", "The Modern Promotheus"], "body": "You will rejoice to hear that no disaster has accompanied the commencement of an enterprise which you have regarded with such evil forebodings. I arrived here yesterday, and my first task is to assure my dear sister of my welfare and increasing confidence in the success of my undertaking." }"#)); - try!(index_writer.add_document(frankenstein_doc)); + index_writer.add_document(frankenstein_doc); @@ -288,7 +288,7 @@ The following document has two titles.

This is an example, so we will only index 3 documents here. You can check out tantivy’s tutorial to index -the English wikipedia. Tantivy’s indexing is rather fast. +the English wikipedia. Tantivy’s indexing is rather fast. Indexing 5 million articles of the English wikipedia takes around 4 minutes on my computer!

@@ -343,15 +343,13 @@ commit.

Searching

-

Let’s search our index. We start -by creating a searcher. There can be more -than one searcher at a time.

-

You should create a searcher -every time you start a “search query”.

+

Let’s search our index. Start by reloading +searchers in the index. This should be done +after every commit().

- 
    let searcher = index.searcher();
+ 
    try!(index.load_searchers());
@@ -362,14 +360,13 @@ every time you start a “search query”.

-

The query parser can interpret human queries. -Here, if the user does not specify which -field they want to search, tantivy will search -in both title and body.

+

Afterwards create one (or more) searchers.

+

You should create a searcher +every time you start a “search query”.

- 
    let query_parser = QueryParser::new(index.schema(), vec!(title, body));
+ 
    let searcher = index.searcher();
@@ -380,6 +377,24 @@ in both title and body.

+

The query parser can interpret human queries. +Here, if the user does not specify which +field they want to search, tantivy will search +in both title and body.

+ + + + 
    let query_parser = QueryParser::new(index.schema(), vec![title, body]);
+ + + + +
  • +
    + +
    + +

    QueryParser may fail if the query is not in the right format. For user facing applications, this can be a problem. A ticket has been opened regarding this problem.

    @@ -391,11 +406,11 @@ A ticket has been opened regarding this problem.

    • -
  • +
  • - +

    A query defines a set of documents, as well as the way they should be scored.

    @@ -408,36 +423,20 @@ any document matching at least one of our terms.

    • -
  • -
    - -
    - -
    -

    Collectors

    -

    We are not interested in all of the documents but -only in the top 10. Keeping track of our top 10 best documents -is the role of the TopCollector.

    - -
    - - 
        
-    let mut top_collector = TopCollector::with_limit(10);
    - -
    • - -
  • -

    We can now perform our query.

    +

    Collectors

    +

    We are not interested in all of the documents but +only in the top 10. Keeping track of our top 10 best documents +is the role of the TopCollector.

    - 
        try!(searcher.search(&query, &mut top_collector)));
    + 
        let mut top_collector = TopCollector::with_limit(10);
    • @@ -448,12 +447,11 @@ is the role of the TopCollector.

    -

    Our top collector now contains the 10 -most relevant doc ids…

    +

    We can now perform our query.

    - 
        let doc_addresses = top_collector.docs();
    + 
        try!(searcher.search(&*query, &mut top_collector));
    @@ -464,7 +462,23 @@ most relevant doc ids…

    -

    The actual documents still need to be +

    Our top collector now contains the 10 +most relevant doc ids…

    + + + + 
        let doc_addresses = top_collector.docs();
    + + + + +
  • +
    + +
    + +
    +

    The actual documents still need to be retrieved from Tantivy’s store.

    Since the body field was not configured as stored, the document returned will only contain @@ -472,10 +486,10 @@ a title.

    - 
        
+            
         for doc_address in doc_addresses {
-         let retrieved_doc = try!(searcher.doc(&doc_address));
-         println!("{}", schema.to_json(&retrieved_doc));
+        let retrieved_doc = try!(searcher.doc(&doc_address));
+        println!("{}", schema.to_json(&retrieved_doc));
     }
 
     Ok(())
diff --git a/examples/simple_search.rs b/examples/simple_search.rs
index cff539b9d..430d7abf0 100644
--- a/examples/simple_search.rs
+++ b/examples/simple_search.rs
@@ -10,105 +10,105 @@ use tantivy::collector::TopCollector;
 use tantivy::query::QueryParser;
 
 fn main() {
-    // Let's create a temporary directory for the 
+    // Let's create a temporary directory for the
     // sake of this example
     if let Ok(dir) = TempDir::new("tantivy_example_dir") {
         run_example(dir.path()).unwrap();
         dir.close().unwrap();
-    }   
+    }
 }
 
 
 fn run_example(index_path: &Path) -> tantivy::Result<()> {
-    
-    
+
+
     // # Defining the schema
     //
     // The Tantivy index requires a very strict schema.
     // The schema declares which fields are in the index,
-    // and for each field, its type and "the way it should 
+    // and for each field, its type and "the way it should
     // be indexed".
-    
-    
+
+
     // first we need to define a schema ...
     let mut schema_builder = SchemaBuilder::default();
-    
+
     // Our first field is title.
     // We want full-text search for it, and we want to be able
     // to retrieve the document after the search.
     //
     // TEXT | STORED is some syntactic sugar to describe
-    // that. 
-    // 
+    // that.
+    //
     // `TEXT` means the field should be tokenized and indexed,
     // along with its term frequency and term positions.
     //
     // `STORED` means that the field will also be saved
     // in a compressed, row-oriented key-value store.
-    // This store is useful to reconstruct the 
+    // This store is useful to reconstruct the
     // documents that were selected during the search phase.
     schema_builder.add_text_field("title", TEXT | STORED);
-    
+
     // Our first field is body.
     // We want full-text search for it, and we want to be able
     // to retrieve the body after the search.
     schema_builder.add_text_field("body", TEXT);
-    
-    let schema = schema_builder.build(); 
+
+    let schema = schema_builder.build();
 
 
 
     // # Indexing documents
     //
     // Let's create a brand new index.
-    // 
+    //
     // This will actually just save a meta.json
     // with our schema in the directory.
     let index = try!(Index::create(index_path, schema.clone()));
 
-    
-    
+
+
     // To insert document we need an index writer.
     // There must be only one writer at a time.
     // This single `IndexWriter` is already
     // multithreaded.
     //
-    // Here we use a buffer of 1 GB. Using a bigger 
+    // Here we use a buffer of 50MB per thread. Using a bigger
     // heap for the indexer can increase its throughput.
-    // This buffer will be split between the indexing
-    // threads.
-    let mut index_writer = try!(index.writer(1_000_000_000));
+    let mut index_writer = try!(index.writer(50_000_000));
 
     // Let's index our documents!
     // We first need a handle on the title and the body field.
-    
-    
+
+
     // ### Create a document "manually".
     //
     // We can create a document manually, by setting the fields
     // one by one in a Document object.
     let title = schema.get_field("title").unwrap();
     let body = schema.get_field("body").unwrap();
-     
+
     let mut old_man_doc = Document::default();
     old_man_doc.add_text(title, "The Old Man and the Sea");
-    old_man_doc.add_text(body, "He was an old man who fished alone in a skiff in the Gulf Stream and he had gone eighty-four days now without taking a fish.");
-    
+    old_man_doc.add_text(body,
+                         "He was an old man who fished alone in a skiff in the Gulf Stream and \
+                          he had gone eighty-four days now without taking a fish.");
+
     // ... and add it to the `IndexWriter`.
-    try!(index_writer.add_document(old_man_doc));
-    
+    index_writer.add_document(old_man_doc);
+
     // ### Create a document directly from json.
     //
     // Alternatively, we can use our schema to parse
     // a document object directly from json.
-    
+
     let mice_and_men_doc = try!(schema.parse_document(r#"{
        "title": "Of Mice and Men",
        "body": "few miles south of Soledad, the Salinas River drops in close to the hillside bank and runs deep and green. The water is warm too, for it has slipped twinkling over the yellow sands in the sunlight before reaching the narrow pool. On one side of the river the golden foothill slopes curve up to the strong and rocky Gabilan Mountains, but on the valley side the water is lined with trees—willows fresh and green with every spring, carrying in their lower leaf junctures the debris of the winter’s flooding; and sycamores with mottled, white,recumbent limbs and branches that arch over the pool"  
     }"#));
-    
-    try!(index_writer.add_document(mice_and_men_doc));
-    
+
+    index_writer.add_document(mice_and_men_doc);
+
     // Multi-valued field are allowed, they are
     // expressed in JSON by an array.
     // The following document has two titles.
@@ -116,20 +116,20 @@ fn run_example(index_path: &Path) -> tantivy::Result<()> {
        "title": ["Frankenstein", "The Modern Promotheus"],
        "body": "You will rejoice to hear that no disaster has accompanied the commencement of an enterprise which you have regarded with such evil forebodings.  I arrived here yesterday, and my first task is to assure my dear sister of my welfare and increasing confidence in the success of my undertaking."  
     }"#));
-    try!(index_writer.add_document(frankenstein_doc));
-    
+    index_writer.add_document(frankenstein_doc);
+
     // This is an example, so we will only index 3 documents
     // here. You can check out tantivy's tutorial to index
-    // the English wikipedia. Tantivy's indexing is rather fast. 
+    // the English wikipedia. Tantivy's indexing is rather fast.
     // Indexing 5 million articles of the English wikipedia takes
     // around 4 minutes on my computer!
-    
-    
+
+
     // ### Committing
-    // 
+    //
     // At this point our documents are not searchable.
     //
-    // 
+    //
     // We need to call .commit() explicitly to force the
     // index_writer to finish processing the documents in the queue,
     // flush the current index to the disk, and advertise
@@ -137,22 +137,25 @@ fn run_example(index_path: &Path) -> tantivy::Result<()> {
     //
     // This call is blocking.
     try!(index_writer.commit());
-    
+
     // If `.commit()` returns correctly, then all of the
     // documents that have been added are guaranteed to be
     // persistently indexed.
-    // 
+    //
     // In the scenario of a crash or a power failure,
     // tantivy behaves as if has rolled back to its last
     // commit.
-    
-    
+
+
     // # Searching
     //
-    // Let's search our index. We start
-    // by creating a searcher. There can be more
-    // than one searcher at a time.
-    // 
+    // Let's search our index. Start by reloading
+    // searchers in the index. This should be done
+    // after every commit().
+    try!(index.load_searchers());
+
+    // Afterwards create one (or more) searchers.
+    //
     // You should create a searcher
     // every time you start a "search query".
     let searcher = index.searcher();
@@ -161,46 +164,45 @@ fn run_example(index_path: &Path) -> tantivy::Result<()> {
     // Here, if the user does not specify which
     // field they want to search, tantivy will search
     // in both title and body.
-    let query_parser = QueryParser::new(index.schema(), vec!(title, body));
-    
+    let query_parser = QueryParser::new(index.schema(), vec![title, body]);
+
     // QueryParser may fail if the query is not in the right
     // format. For user facing applications, this can be a problem.
     // A ticket has been opened regarding this problem.
     let query = try!(query_parser.parse_query("sea whale"));
-    
-    
+
+
     // A query defines a set of documents, as
     // well as the way they should be scored.
-    //  
+    //
     // A query created by the query parser is scored according
     // to a metric called Tf-Idf, and will consider
     // any document matching at least one of our terms.
-    
-    // ### Collectors 
+
+    // ### Collectors
     //
-    // We are not interested in all of the documents but 
+    // We are not interested in all of the documents but
     // only in the top 10. Keeping track of our top 10 best documents
     // is the role of the TopCollector.
-    
     let mut top_collector = TopCollector::with_limit(10);
-    
+
     // We can now perform our query.
     try!(searcher.search(&*query, &mut top_collector));
 
-    // Our top collector now contains the 10 
+    // Our top collector now contains the 10
     // most relevant doc ids...
     let doc_addresses = top_collector.docs();
 
-    // The actual documents still need to be 
+    // The actual documents still need to be
     // retrieved from Tantivy's store.
-    // 
+    //
     // Since the body field was not configured as stored,
     // the document returned will only contain
     // a title.
-    
+
     for doc_address in doc_addresses {
-         let retrieved_doc = try!(searcher.doc(&doc_address));
-         println!("{}", schema.to_json(&retrieved_doc));
+        let retrieved_doc = try!(searcher.doc(&doc_address));
+        println!("{}", schema.to_json(&retrieved_doc));
     }
 
     Ok(())
diff --git a/src/collector/chained_collector.rs b/src/collector/chained_collector.rs
index 5840eb775..524ffec58 100644
--- a/src/collector/chained_collector.rs
+++ b/src/collector/chained_collector.rs
@@ -1,7 +1,7 @@
+use Result;
 use collector::Collector;
 use SegmentLocalId;
 use SegmentReader;
-use std::io;
 use DocId;
 use Score;
 
@@ -12,7 +12,7 @@ use Score;
 pub struct DoNothingCollector;
 impl Collector for DoNothingCollector {
     #[inline]
-    fn set_segment(&mut self, _: SegmentLocalId, _: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, _: SegmentLocalId, _: &SegmentReader) -> Result<()> {
         Ok(())
     }
     #[inline]
@@ -38,7 +38,7 @@ impl ChainedCollector {
 }
 
 impl Collector for ChainedCollector {
-    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> Result<()> {
         try!(self.left.set_segment(segment_local_id, segment));
         try!(self.right.set_segment(segment_local_id, segment));
         Ok(())
diff --git a/src/collector/count_collector.rs b/src/collector/count_collector.rs
index 8a9014a25..ff15abd73 100644
--- a/src/collector/count_collector.rs
+++ b/src/collector/count_collector.rs
@@ -1,7 +1,7 @@
-use std::io;
 use super::Collector;
 use DocId;
 use Score;
+use Result;
 use SegmentReader;
 use SegmentLocalId;
 
@@ -28,7 +28,7 @@ impl Default for CountCollector {
 
 impl Collector for CountCollector {
 
-    fn set_segment(&mut self, _: SegmentLocalId, _: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, _: SegmentLocalId, _: &SegmentReader) -> Result<()> {
         Ok(())
     }
 
diff --git a/src/collector/mod.rs b/src/collector/mod.rs
index 84bc38485..75c22aded 100644
--- a/src/collector/mod.rs
+++ b/src/collector/mod.rs
@@ -2,7 +2,7 @@ use SegmentReader;
 use SegmentLocalId;
 use DocId;
 use Score;
-use std::io;
+use Result;
 
 mod count_collector;
 pub use self::count_collector::CountCollector;
@@ -48,14 +48,14 @@ pub use self::chained_collector::chain;
 pub trait Collector {
     /// `set_segment` is called before beginning to enumerate 
     /// on this segment.
-    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> io::Result<()>;
+    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> Result<()>;
     /// The query pushes the scored document to the collector via this method.
     fn collect(&mut self, doc: DocId, score: Score);
 }
 
 
 impl<'a, C: Collector> Collector for &'a mut C {
-    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> Result<()> {
         (*self).set_segment(segment_local_id, segment)
     }
     /// The query pushes the scored document to the collector via this method.
@@ -73,7 +73,6 @@ pub mod tests {
     use DocId;
     use Score;
     use core::SegmentReader;
-    use std::io;
     use SegmentLocalId;
     use fastfield::U32FastFieldReader;
     use schema::Field;
@@ -107,7 +106,7 @@ pub mod tests {
 
     impl Collector for TestCollector {
 
-        fn set_segment(&mut self, _: SegmentLocalId, reader: &SegmentReader) -> io::Result<()> {
+        fn set_segment(&mut self, _: SegmentLocalId, reader: &SegmentReader) -> Result<()> {
             self.offset += self.segment_max_doc;
             self.segment_max_doc = reader.max_doc();
             Ok(())
@@ -140,14 +139,14 @@ pub mod tests {
             }
         }
 
-        pub fn vals(&self,) -> &Vec {
-            &self.vals
+        pub fn vals(self,) -> Vec {
+            self.vals
         }
     }
         
     impl Collector for FastFieldTestCollector {
-        fn set_segment(&mut self, _: SegmentLocalId, reader: &SegmentReader) -> io::Result<()> {
-            self.ff_reader = Some(try!(reader.get_fast_field_reader(self.field)));
+        fn set_segment(&mut self, _: SegmentLocalId, reader: &SegmentReader) -> Result<()> {
+            self.ff_reader = reader.get_fast_field_reader(self.field);
             Ok(())
         }
 
diff --git a/src/collector/multi_collector.rs b/src/collector/multi_collector.rs
index 6ce999e80..e5eddc7f4 100644
--- a/src/collector/multi_collector.rs
+++ b/src/collector/multi_collector.rs
@@ -1,7 +1,7 @@
-use std::io;
 use super::Collector;
 use DocId;
 use Score;
+use Result;
 use SegmentReader;
 use SegmentLocalId;
 
@@ -25,7 +25,7 @@ impl<'a> MultiCollector<'a> {
 
 
 impl<'a> Collector for MultiCollector<'a> {
-    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, segment_local_id: SegmentLocalId, segment: &SegmentReader) -> Result<()> {
         for collector in &mut self.collectors {
             try!(collector.set_segment(segment_local_id, segment));
         }
diff --git a/src/collector/top_collector.rs b/src/collector/top_collector.rs
index 21c023caf..6425eb300 100644
--- a/src/collector/top_collector.rs
+++ b/src/collector/top_collector.rs
@@ -1,8 +1,8 @@
-use std::io;
 use super::Collector;
 use SegmentReader;
 use SegmentLocalId;
 use DocAddress;
+use Result;
 use std::collections::BinaryHeap;
 use std::cmp::Ordering;
 use DocId;
@@ -105,7 +105,7 @@ impl TopCollector {
 
 impl Collector for TopCollector {
 
-    fn set_segment(&mut self, segment_id: SegmentLocalId, _: &SegmentReader) -> io::Result<()> {
+    fn set_segment(&mut self, segment_id: SegmentLocalId, _: &SegmentReader) -> Result<()> {
         self.segment_id = segment_id;
         Ok(())
     }
diff --git a/src/common/mod.rs b/src/common/mod.rs
index b0835c082..4812b8700 100644
--- a/src/common/mod.rs
+++ b/src/common/mod.rs
@@ -4,6 +4,7 @@ mod vint;
 pub mod bitpacker;
 mod counting_writer;
 
+
 pub use self::serialize::BinarySerializable;
 pub use self::timer::Timing;
 pub use self::timer::TimerTree;
@@ -13,6 +14,7 @@ pub use self::counting_writer::CountingWriter;
 
 use std::io;
 
+/// Create a default io error given a string.
 pub fn make_io_err(msg: String) -> io::Error {
     io::Error::new(io::ErrorKind::Other, msg)
 }
@@ -30,3 +32,14 @@ pub trait HasLen {
 }
 
 
+/// Creates an uninitialized Vec of a given usize
+///
+/// `allocate_vec` does an unsafe call to `set_len`
+/// as other solution are extremely slow in debug mode.
+pub fn allocate_vec(capacity: usize) -> Vec {
+    let mut v = Vec::with_capacity(capacity);
+    unsafe {
+        v.set_len(capacity);
+    }
+    v
+}
diff --git a/src/common/serialize.rs b/src/common/serialize.rs
index b1ffab6cd..6bd1426fe 100644
--- a/src/common/serialize.rs
+++ b/src/common/serialize.rs
@@ -74,7 +74,6 @@ impl BinarySerializable for u64 {
 
 impl BinarySerializable for u8 {
     fn serialize(&self, writer: &mut Write) -> io::Result {
-        // TODO error
         try!(writer.write_u8(*self));
         Ok(1)
     }
diff --git a/src/compression/compression_simd.rs b/src/compression/compression_simd.rs
index 605d0ec03..308e13445 100644
--- a/src/compression/compression_simd.rs
+++ b/src/compression/compression_simd.rs
@@ -1,44 +1,45 @@
-
 use super::NUM_DOCS_PER_BLOCK;
 
-use libc::size_t;
-
 const COMPRESSED_BLOCK_MAX_SIZE: usize = NUM_DOCS_PER_BLOCK * 4 + 1; 
 
-extern {
-    fn compress_sorted_cpp(
-        data: *const u32,
-        output: *mut u8,
-        offset: u32) -> size_t;
+mod simdcomp {
+    use libc::size_t;
 
-    fn uncompress_sorted_cpp(
-        compressed_data: *const u8,
-        output: *mut u32,
-        offset: u32) -> size_t;
-        
-    fn compress_unsorted_cpp(
-        data: *const u32,
-        output: *mut u8) -> size_t;
+    extern {
+        pub fn compress_sorted(
+            data: *const u32,
+            output: *mut u8,
+            offset: u32) -> size_t;
 
-    fn uncompress_unsorted_cpp(
-        compressed_data: *const u8,
-        output: *mut u32) -> size_t;
+        pub fn uncompress_sorted(
+            compressed_data: *const u8,
+            output: *mut u32,
+            offset: u32) -> size_t;
+            
+        pub fn compress_unsorted(
+            data: *const u32,
+            output: *mut u8) -> size_t;
+
+        pub fn uncompress_unsorted(
+            compressed_data: *const u8,
+            output: *mut u32) -> size_t;
+    }
 }
 
 fn compress_sorted(vals: &[u32], output: &mut [u8], offset: u32) -> usize {
-    unsafe { compress_sorted_cpp(vals.as_ptr(), output.as_mut_ptr(), offset) }
+    unsafe { simdcomp::compress_sorted(vals.as_ptr(), output.as_mut_ptr(), offset) }
 }
 
 fn uncompress_sorted(compressed_data: &[u8], output: &mut [u32], offset: u32) -> usize {
-    unsafe { uncompress_sorted_cpp(compressed_data.as_ptr(), output.as_mut_ptr(), offset) }
+    unsafe { simdcomp::uncompress_sorted(compressed_data.as_ptr(), output.as_mut_ptr(), offset) }
 }
 
 fn compress_unsorted(vals: &[u32], output: &mut [u8]) -> usize {
-    unsafe { compress_unsorted_cpp(vals.as_ptr(), output.as_mut_ptr()) }
+    unsafe { simdcomp::compress_unsorted(vals.as_ptr(), output.as_mut_ptr()) }
 }
 
 fn uncompress_unsorted(compressed_data: &[u8], output: &mut [u32]) -> usize {
-    unsafe { uncompress_unsorted_cpp(compressed_data.as_ptr(), output.as_mut_ptr()) }
+    unsafe { simdcomp::uncompress_unsorted(compressed_data.as_ptr(), output.as_mut_ptr()) }
 }
 
 
diff --git a/src/core/index.rs b/src/core/index.rs
index d29cc1fc3..cb97ba569 100644
--- a/src/core/index.rs
+++ b/src/core/index.rs
@@ -2,59 +2,53 @@ use Result;
 use Error;
 use schema::Schema;
 use std::sync::Arc;
+use std::borrow::BorrowMut;
 use std::fmt;
 use rustc_serialize::json;
 use core::SegmentId;
 use directory::{Directory, MmapDirectory, RAMDirectory};
-use indexer::IndexWriter;
+use indexer::index_writer::open_index_writer;
 use core::searcher::Searcher;
 use std::convert::From;
 use num_cpus;
 use super::segment::Segment;
 use core::SegmentReader;
 use super::pool::Pool;
+use core::SegmentMeta;
 use super::pool::LeasedItem;
 use std::path::Path;
-use indexer::SegmentManager;
 use core::IndexMeta;
+use IndexWriter;
+use directory::ManagedDirectory;
 use core::META_FILEPATH;
 use super::segment::create_segment;
 use indexer::segment_updater::save_new_metas;
 
 const NUM_SEARCHERS: usize = 12;
 
-/// Accessor to the index segment manager
-///
-/// This method is not part of tantivy's public API
-pub fn get_segment_manager(index: &Index) -> Arc {
-    index.segment_manager.clone()
-}
-
-
 fn load_metas(directory: &Directory) -> Result {
-    let meta_file = try!(directory.open_read(&META_FILEPATH));
-    let meta_content = String::from_utf8_lossy(meta_file.as_slice());
-    json::decode(&meta_content)
+    let meta_data = directory.atomic_read(&META_FILEPATH)?;
+    let meta_string = String::from_utf8_lossy(&meta_data);
+    json::decode(&meta_string)
         .map_err(|e| Error::CorruptedFile(META_FILEPATH.clone(), Box::new(e)))
 }
 
 /// Tantivy's Search Index
 pub struct Index {
-    segment_manager: Arc,
-
-    directory: Box,
+    directory: ManagedDirectory,
     schema: Schema,
     searcher_pool: Arc>,
-    docstamp: u64,
 }
 
+
 impl Index {
     /// Creates a new index using the `RAMDirectory`.
     ///
     /// The index will be allocated in anonymous memory.
     /// This should only be used for unit tests.
     pub fn create_in_ram(schema: Schema) -> Index {
-        let directory = Box::new(RAMDirectory::create());
+        let ram_directory = RAMDirectory::create();
+        let directory = ManagedDirectory::new(ram_directory).expect("Creating a managed directory from a brand new RAM directory should never fail.");
         Index::from_directory(directory, schema).expect("Creating a RAMDirectory should never fail") // unwrap is ok here
     }
 
@@ -63,9 +57,9 @@ impl Index {
     ///
     /// If a previous index was in this directory, then its meta file will be destroyed.
     pub fn create(directory_path: &Path, schema: Schema) -> Result {
-        let mut directory = MmapDirectory::open(directory_path)?;
-        save_new_metas(schema.clone(), 0, &mut directory)?;
-        Index::from_directory(box directory, schema)
+        let mmap_directory = MmapDirectory::open(directory_path)?;
+        let directory = ManagedDirectory::new(mmap_directory)?;
+        Index::from_directory(directory, schema)
     }
 
     /// Creates a new index in a temp directory.
@@ -77,49 +71,55 @@ impl Index {
     /// The temp directory is only used for testing the `MmapDirectory`.
     /// For other unit tests, prefer the `RAMDirectory`, see: `create_in_ram`.
     pub fn create_from_tempdir(schema: Schema) -> Result {
-        let directory = Box::new(try!(MmapDirectory::create_from_tempdir()));
+        let mmap_directory = MmapDirectory::create_from_tempdir()?;
+        let directory = ManagedDirectory::new(mmap_directory)?;
         Index::from_directory(directory, schema)
     }
 
     /// Creates a new index given a directory and an `IndexMeta`.
-    fn create_from_metas(directory: Box, metas: IndexMeta) -> Result {
+    fn create_from_metas(directory: ManagedDirectory, metas: IndexMeta) -> Result {
         let schema = metas.schema.clone();
-        let docstamp = metas.docstamp;
-        let committed_segments = metas.committed_segments;
-        // TODO log somethings is uncommitted is not empty.
         let index = Index {
-            segment_manager: Arc::new(SegmentManager::from_segments(committed_segments)),
             directory: directory,
             schema: schema,
             searcher_pool: Arc::new(Pool::new()),
-            docstamp: docstamp,
         };
         try!(index.load_searchers());
         Ok(index)
     }
 
-    /// Opens a new directory from a directory.
-    pub fn from_directory(directory: Box, schema: Schema) -> Result {
+    /// Create a new index from a directory.
+    pub fn from_directory(mut directory: ManagedDirectory, schema: Schema) -> Result {
+        save_new_metas(schema.clone(), 0, directory.borrow_mut())?;
         Index::create_from_metas(directory, IndexMeta::with_schema(schema))
     }
 
     /// Opens a new directory from an index path.
     pub fn open(directory_path: &Path) -> Result {
-        let directory = try!(MmapDirectory::open(directory_path));
-        let metas = try!(load_metas(&directory)); //< TODO does the directory already exists?
-        Index::create_from_metas(directory.box_clone(), metas)
+        let mmap_directory = MmapDirectory::open(directory_path)?;
+        let directory = ManagedDirectory::new(mmap_directory)?;
+        let metas = try!(load_metas(&directory));
+        Index::create_from_metas(directory, metas)
     }
 
-    /// Returns the index docstamp.
+    /// Returns the index opstamp.
     ///
-    /// The docstamp is the number of documents that have been added
+    /// The opstamp is the number of documents that have been added
     /// from the beginning of time, and until the moment of the last commit.
-    pub fn docstamp(&self) -> u64 {
-        self.docstamp
+    pub fn opstamp(&self) -> u64 {
+        load_metas(self.directory()).unwrap().opstamp
     }
 
-    /// Creates a multithreaded writer.
-    /// Each writer produces an independent segment.
+    /// Open a new index writer. Attempts to acquire a lockfile.
+    ///
+    /// The lockfile should be deleted on drop, but it is possible
+    /// that due to a panic or other error, a stale lockfile will be
+    /// left in the index directory. If you are sure that no other
+    /// `IndexWriter` on the system is accessing the index directory,
+    /// it is safe to manually delete the lockfile.
+    ///
+    /// num_threads specifies the number of indexing workers that
+    /// should work at the same time.
     ///
     /// # Errors
     /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
@@ -129,12 +129,13 @@ impl Index {
                                    num_threads: usize,
                                    heap_size_in_bytes: usize)
                                    -> Result {
-        IndexWriter::open(self, num_threads, heap_size_in_bytes)
+        open_index_writer(self, num_threads, heap_size_in_bytes)
     }
 
 
     /// Creates a multithreaded writer
     /// It just calls `writer_with_num_threads` with the number of cores as `num_threads`
+    ///
     /// # Errors
     /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
     /// # Panics
@@ -151,47 +152,47 @@ impl Index {
     }
 
     /// Returns the list of segments that are searchable
-    pub fn searchable_segments(&self) -> Vec {
-        self.searchable_segment_ids()
+    pub fn searchable_segments(&self) -> Result> {
+        Ok(self
+            .searchable_segment_metas()?
             .into_iter()
-            .map(|segment_id| self.segment(segment_id))
-            .collect()
+            .map(|segment_meta| self.segment(segment_meta))
+            .collect())
     }
 
-    /// Remove all of the file associated with the segment.
-    ///
-    /// This method cannot fail. If a problem occurs,
-    /// some files may end up never being removed.
-    /// The error will only be logged.
-    pub fn delete_segment(&self, segment_id: SegmentId) {
-        self.segment(segment_id).delete();
-    }
-
-    /// Return a segment object given a `segment_id`
-    ///
-    /// The segment may or may not exist.
-    pub fn segment(&self, segment_id: SegmentId) -> Segment {
-        create_segment(self.clone(), segment_id)
-    }
-
-    /// Return a reference to the index directory.
-    pub fn directory(&self) -> &Directory {
-        &*self.directory
-    }
-
-    /// Return a mutable reference to the index directory.
-    pub fn directory_mut(&mut self) -> &mut Directory {
-        &mut *self.directory
-    }
-
-    /// Returns the list of segment ids that are searchable.
-    fn searchable_segment_ids(&self) -> Vec {
-        self.segment_manager.committed_segments()
+    #[doc(hidden)]
+    pub fn segment(&self, segment_meta: SegmentMeta) -> Segment {
+        create_segment(self.clone(), segment_meta)
     }
 
     /// Creates a new segment.
     pub fn new_segment(&self) -> Segment {
-        self.segment(SegmentId::generate_random())
+        let segment_meta = SegmentMeta::new(SegmentId::generate_random());
+        create_segment(self.clone(), segment_meta)
+    }
+
+    /// Return a reference to the index directory.
+    pub fn directory(&self) -> &ManagedDirectory {
+        &self.directory
+    }
+
+    /// Return a mutable reference to the index directory.
+    pub fn directory_mut(&mut self) -> &mut ManagedDirectory {
+        &mut self.directory
+    }
+
+    /// Reads the meta.json and returns the list of
+    /// `SegmentMeta` from the last commit.
+    pub fn searchable_segment_metas(&self) -> Result> {
+        Ok(load_metas(self.directory())?.segments)
+    }
+    
+    /// Returns the list of segment ids that are searchable.
+    pub fn searchable_segment_ids(&self) -> Result> {
+        Ok(self.searchable_segment_metas()?
+               .iter()
+               .map(|segment_meta| segment_meta.id())
+               .collect())          
     }
 
     /// Creates a new generation of searchers after
@@ -200,16 +201,14 @@ impl Index {
     /// This needs to be called when a new segment has been
     /// published or after a merge.
     pub fn load_searchers(&self) -> Result<()> {
-        let searchable_segments = self.searchable_segments();
-        let mut searchers = Vec::new();
-        for _ in 0..NUM_SEARCHERS {
-            let searchable_segments_clone = searchable_segments.clone();
-            let segment_readers: Vec = try!(searchable_segments_clone.into_iter()
+        let searchable_segments = self.searchable_segments()?;
+        let segment_readers: Vec = try!(searchable_segments
+                .into_iter()
                 .map(SegmentReader::open)
                 .collect());
-            let searcher = Searcher::from(segment_readers);
-            searchers.push(searcher);
-        }
+        let searchers = (0..NUM_SEARCHERS)
+            .map(|_| Searcher::from(segment_readers.clone()))
+            .collect();
         self.searcher_pool.publish_new_generation(searchers);
         Ok(())
     }
@@ -239,12 +238,9 @@ impl fmt::Debug for Index {
 impl Clone for Index {
     fn clone(&self) -> Index {
         Index {
-            segment_manager: self.segment_manager.clone(),
-
-            directory: self.directory.box_clone(),
+            directory: self.directory.clone(),
             schema: self.schema.clone(),
             searcher_pool: self.searcher_pool.clone(),
-            docstamp: self.docstamp,
         }
     }
 }
diff --git a/src/core/index_meta.rs b/src/core/index_meta.rs
index a2623f9d0..8a0274b4e 100644
--- a/src/core/index_meta.rs
+++ b/src/core/index_meta.rs
@@ -1,7 +1,5 @@
-
 use schema::Schema;
-use core::SegmentId;
-
+use core::SegmentMeta;
 
 /// Meta information about the `Index`.
 /// 
@@ -13,35 +11,17 @@ use core::SegmentId;
 ///
 #[derive(Clone,Debug,RustcDecodable,RustcEncodable)]
 pub struct IndexMeta {
-    pub committed_segments: Vec,
-    pub uncommitted_segments: Vec,
+    pub segments: Vec,
     pub schema: Schema,
-    pub docstamp: u64,
+    pub opstamp: u64,
 }
 
 impl IndexMeta {
     pub fn with_schema(schema: Schema) -> IndexMeta {
         IndexMeta {
-            committed_segments: Vec::new(),
-            uncommitted_segments: Vec::new(),
+            segments: vec!(),
             schema: schema,
-            docstamp: 0u64,
+            opstamp: 0u64,
         }
     }
 }
-
-#[derive(Clone, Debug, RustcDecodable,RustcEncodable)]
-pub struct SegmentMeta {
-    pub segment_id: SegmentId,
-    pub num_docs: u32,
-}
-
-#[cfg(test)]
-impl SegmentMeta {
-    pub fn new(segment_id: SegmentId, num_docs: u32) -> SegmentMeta {
-        SegmentMeta {
-            segment_id: segment_id,
-            num_docs: num_docs,
-        }
-    }
-}
\ No newline at end of file
diff --git a/src/core/mod.rs b/src/core/mod.rs
index 2dfac69d1..6f7cb9edc 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -1,5 +1,4 @@
 pub mod searcher;
-
 pub mod index;
 mod segment_reader;
 mod segment_id;
@@ -7,20 +6,38 @@ mod segment_component;
 mod segment;
 mod index_meta;
 mod pool;
+mod segment_meta;
 mod term_iterator;
 
-use std::path::PathBuf;
-
+pub use self::searcher::Searcher;
 pub use self::segment_component::SegmentComponent;
 pub use self::segment_id::SegmentId;
 pub use self::segment_reader::SegmentReader;
 pub use self::segment::Segment;
-pub use self::segment::SegmentInfo;
 pub use self::segment::SerializableSegment;
 pub use self::index::Index;
-pub use self::index_meta::{IndexMeta, SegmentMeta};
+pub use self::segment_meta::SegmentMeta;
+pub use self::index_meta::IndexMeta;
 pub use self::term_iterator::TermIterator;
 
+
+use std::path::PathBuf;
+
 lazy_static! {
+    /// The meta file contains all the information about the list of segments and the schema
+    /// of the index.
     pub static ref META_FILEPATH: PathBuf = PathBuf::from("meta.json");
+    
+    /// The managed file contains a list of files that were created by the tantivy
+    /// and will therefore be garbage collected when they are deemed useless by tantivy.
+    ///
+    /// Removing this file is safe, but will prevent the garbage collection of all of the file that
+    /// are currently in the directory
+    pub static ref MANAGED_FILEPATH: PathBuf = PathBuf::from(".managed.json");
+
+    /// Only one process should be able to write tantivy's index at a time.
+    /// This file, when present, is in charge of preventing other processes to open an IndexWriter.
+    ///
+    /// If the process is killed and this file remains, it is safe to remove it manually.
+    pub static ref LOCKFILE_FILEPATH: PathBuf = PathBuf::from(".tantivy-indexer.lock");
 }
\ No newline at end of file
diff --git a/src/core/searcher.rs b/src/core/searcher.rs
index 0d99a2897..839e00172 100644
--- a/src/core/searcher.rs
+++ b/src/core/searcher.rs
@@ -8,6 +8,7 @@ use DocId;
 use DocAddress;
 use schema::Term;
 use core::TermIterator;
+use std::fmt;
 
 
 /// Holds a list of `SegmentReader`s ready for search.
@@ -15,13 +16,13 @@ use core::TermIterator;
 /// It guarantees that the `Segment` will not be removed before  
 /// the destruction of the `Searcher`.
 /// 
-#[derive(Debug)]
 pub struct Searcher {
     segment_readers: Vec,
 }
 
+
 impl Searcher {
-      
+
     /// Fetches a document from tantivy's store given a `DocAddress`.
     ///
     /// The searcher uses the segment ordinal to route the
@@ -83,4 +84,14 @@ impl From> for Searcher {
             segment_readers: segment_readers,
         }
     }
+}
+
+impl fmt::Debug for Searcher {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let segment_ids = self.segment_readers
+            .iter()
+            .map(|segment_reader| segment_reader.segment_id())
+            .collect::>();
+        write!(f, "Searcher({:?})", segment_ids)
+    }
 }
\ No newline at end of file
diff --git a/src/core/segment.rs b/src/core/segment.rs
index 3e8bc9a42..c99d36e85 100644
--- a/src/core/segment.rs
+++ b/src/core/segment.rs
@@ -1,97 +1,89 @@
 use Result;
 use std::path::PathBuf;
 use schema::Schema;
-use DocId;
 use std::fmt;
 use core::SegmentId;
-use directory::{ReadOnlySource, WritePtr};
+use directory::{ReadOnlySource, WritePtr, FileProtection};
 use indexer::segment_serializer::SegmentSerializer;
 use super::SegmentComponent;
 use core::Index;
 use std::result;
-use directory::error::{FileError, OpenWriteError};
-
-
+use directory::Directory;
+use core::SegmentMeta;
+use directory::error::{OpenReadError, OpenWriteError};
 
 /// A segment is a piece of the index.
 #[derive(Clone)]
 pub struct Segment {
     index: Index,
-    segment_id: SegmentId,
+    meta: SegmentMeta,
 }
 
 impl fmt::Debug for Segment {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Segment({:?})", self.segment_id.uuid_string())
+        write!(f, "Segment({:?})", self.id().uuid_string())
     }
 }
 
-
 /// Creates a new segment given an `Index` and a `SegmentId`
 /// 
 /// The function is here to make it private outside `tantivy`. 
-pub fn create_segment(index: Index, segment_id: SegmentId) -> Segment {
+pub fn create_segment(index: Index, meta: SegmentMeta) -> Segment {
     Segment {
         index: index,
-        segment_id: segment_id,
+        meta: meta,
     }
 }
 
 impl Segment {
-
-
+    
     /// Returns our index's schema.
     pub fn schema(&self,) -> Schema {
         self.index.schema()
     }
 
+    /// Returns the segment meta-information
+    pub fn meta(&self) -> &SegmentMeta {
+        &self.meta
+    }
+
+    #[doc(hidden)]
+    pub fn set_delete_meta(&mut self, num_deleted_docs: u32, opstamp: u64) {
+        self.meta.set_delete_meta(num_deleted_docs, opstamp);
+    }
+
     /// Returns the segment's id.
     pub fn id(&self,) -> SegmentId {
-        self.segment_id
+        self.meta.id()
     }
-    
 
     /// Returns the relative path of a component of our segment.
     ///  
     /// It just joins the segment id with the extension 
     /// associated to a segment component.
     pub fn relative_path(&self, component: SegmentComponent) -> PathBuf {
-        self.segment_id.relative_path(component)
+        self.meta.relative_path(component)
     }
 
-    /// Deletes all of the document of the segment.
-    /// This is called when there is a merge or a rollback.
+
+    /// Protects a specific component file from being deleted.
     ///
-    /// # Disclaimer
-    /// If deletion of a file fails (e.g. a file 
-    /// was read-only.), the method does not
-    /// fail and just logs an error
-    pub fn delete(&self,) {
-        for component in SegmentComponent::values() {
-            let rel_path = self.relative_path(component);
-            if let Err(err) = self.index.directory().delete(&rel_path) {
-                match err {
-                    FileError::FileDoesNotExist(_) => {
-                        // this is normal behavior.
-                        // the position file for instance may not exists.
-                    }
-                    FileError::IOError(err) => {
-                		error!("Failed to remove {:?} : {:?}", self.segment_id, err);
-                    }
-                }
-            }
-        }
+    /// Returns a FileProtection object. The file is guaranteed
+    /// to not be garbage collected as long as this `FileProtection`  object
+    /// lives.
+    pub fn protect_from_delete(&self, component: SegmentComponent) -> FileProtection {
+        let path = self.relative_path(component);
+        self.index.directory().protect_file_from_delete(&path)
     }
 
-
-    /// Open one of the component file for read.
-    pub fn open_read(&self, component: SegmentComponent) -> result::Result {
+    /// Open one of the component file for a *regular* read.
+    pub fn open_read(&self, component: SegmentComponent) -> result::Result {
         let path = self.relative_path(component);
         let source = try!(self.index.directory().open_read(&path));
         Ok(source)
     }
 
-    /// Open one of the component file for write.
+    /// Open one of the component file for *regular* write.
     pub fn open_write(&mut self, component: SegmentComponent) -> result::Result {
         let path = self.relative_path(component);
         let write = try!(self.index.directory_mut().open_write(&path));
@@ -108,7 +100,34 @@ pub trait SerializableSegment {
     fn write(&self, serializer: SegmentSerializer) -> Result;
 }
 
-#[derive(Clone,Debug,RustcDecodable,RustcEncodable)]
-pub struct SegmentInfo {
-	pub max_doc: DocId,
+#[cfg(test)]
+mod tests {
+
+    use core::SegmentComponent;
+    use directory::Directory;
+    use std::collections::HashSet;
+    use schema::SchemaBuilder;
+    use Index;
+
+    #[test]
+    fn test_segment_protect_component() {
+        let mut index = Index::create_in_ram(SchemaBuilder::new().build());
+        let segment = index.new_segment();
+        let path = segment.relative_path(SegmentComponent::POSTINGS);
+        
+        let directory = index.directory_mut();
+        directory.atomic_write(&*path, &vec!(0u8)).unwrap();
+        
+        let living_files = HashSet::new();
+        {
+            let _file_protection = segment.protect_from_delete(SegmentComponent::POSTINGS);
+            assert!(directory.exists(&*path));
+            directory.garbage_collect(living_files.clone());
+            assert!(directory.exists(&*path));
+        }
+
+        directory.garbage_collect(living_files);
+        assert!(!directory.exists(&*path));
+    }
+
 }
\ No newline at end of file
diff --git a/src/core/segment_component.rs b/src/core/segment_component.rs
index a55ea19dc..6f85c4031 100644
--- a/src/core/segment_component.rs
+++ b/src/core/segment_component.rs
@@ -1,41 +1,27 @@
-use std::vec::IntoIter;
-
 #[derive(Copy, Clone)]
 pub enum SegmentComponent {
-    INFO,
     POSTINGS,
     POSITIONS,
     FASTFIELDS,
     FIELDNORMS,
     TERMS,
     STORE,
+    DELETE
 }
 
 impl SegmentComponent {
-    pub fn values() -> IntoIter {
-        vec!(
-            SegmentComponent::INFO,
+    
+    pub fn iterator() -> impl Iterator {
+        static SEGMENT_COMPONENTS: [SegmentComponent;  7] = [
             SegmentComponent::POSTINGS,
             SegmentComponent::POSITIONS,
             SegmentComponent::FASTFIELDS,
             SegmentComponent::FIELDNORMS,
             SegmentComponent::TERMS,
             SegmentComponent::STORE,
-        ).into_iter()
+            SegmentComponent::DELETE
+        ];
+        SEGMENT_COMPONENTS.into_iter()
     }
     
-    pub fn path_suffix(&self)-> &'static str {
-        match *self {
-            SegmentComponent::POSITIONS => ".pos",
-            SegmentComponent::INFO => ".info",
-            SegmentComponent::POSTINGS => ".idx",
-            SegmentComponent::TERMS => ".term",
-            SegmentComponent::STORE => ".store",
-            SegmentComponent::FASTFIELDS => ".fast",
-            SegmentComponent::FIELDNORMS => ".fieldnorm",
-        }
-    }
-}
-
-
-    
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/src/core/segment_id.rs b/src/core/segment_id.rs
index 3d77668b3..9e3a75d3d 100644
--- a/src/core/segment_id.rs
+++ b/src/core/segment_id.rs
@@ -1,14 +1,19 @@
 use uuid::Uuid;
 use std::fmt;
 use rustc_serialize::{Encoder, Decoder, Encodable, Decodable};
-use core::SegmentComponent;
-use std::path::PathBuf;
 use std::cmp::{Ordering, Ord};
 
-
 #[cfg(test)]
 use std::sync::atomic;
 
+/// Tantivy SegmentId.
+///
+/// Tantivy's segment are identified 
+/// by a UUID which is used to prefix the filenames
+/// of all of the file associated with the segment.
+///
+/// In unit test, for reproducability, the SegmentId are
+/// simply generated in an autoincrement fashion.
 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 pub struct SegmentId(Uuid);
 
@@ -37,22 +42,27 @@ fn create_uuid() -> Uuid {
 }
 
 impl SegmentId {
+    #[doc(hidden)]
     pub fn generate_random() -> SegmentId {
         SegmentId(create_uuid())
     }
 
+
+    /// Returns a shorter identifier of the segment.
+    ///
+    /// We are using UUID4, so only 6 bits are fixed,
+    /// and the rest is random.
+    ///
+    /// Picking the first 8 chars is ok to identify 
+    /// segments in a display message.
     pub fn short_uuid_string(&self,) -> String {
         (&self.0.simple().to_string()[..8]).to_string()
     }
 
+    /// Returns a segment uuid string.
     pub fn uuid_string(&self,) -> String {
         self.0.simple().to_string()
     }
-
-    pub fn relative_path(&self, component: SegmentComponent) -> PathBuf {
-        let filename = self.uuid_string() + component.path_suffix();
-        PathBuf::from(filename)
-    }
 }
 
 impl Encodable for SegmentId {
@@ -69,7 +79,7 @@ impl Decodable for SegmentId {
 
 impl fmt::Debug for SegmentId {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "SegmentId({:?})", self.uuid_string())
+        write!(f, "Seg({:?})", self.short_uuid_string())
     }
 }
 
diff --git a/src/core/segment_meta.rs b/src/core/segment_meta.rs
new file mode 100644
index 000000000..9716c348b
--- /dev/null
+++ b/src/core/segment_meta.rs
@@ -0,0 +1,121 @@
+use core::SegmentId;
+use super::SegmentComponent;
+use std::path::PathBuf;
+use std::collections::HashSet;
+
+#[derive(Clone, Debug, RustcDecodable,RustcEncodable)]
+struct DeleteMeta {
+    num_deleted_docs: u32,
+    opstamp: u64,
+}
+
+/// SegmentMeta contains simple meta information about a segment.
+///
+/// For instance the number of docs it contains,
+/// how many are deleted, etc.
+#[derive(Clone, Debug, RustcDecodable,RustcEncodable)]
+pub struct SegmentMeta {
+    segment_id: SegmentId,
+    max_doc: u32,
+    deletes: Option, 
+}
+
+impl SegmentMeta {
+
+    /// Creates a new segment meta for 
+    /// a segment with no deletes and no documents.
+    pub fn new(segment_id: SegmentId) -> SegmentMeta {
+        SegmentMeta {
+            segment_id: segment_id,
+            max_doc: 0,
+            deletes: None,
+        }
+    }
+
+    /// Returns the segment id.
+    pub fn id(&self) -> SegmentId {
+        self.segment_id
+    }
+
+    /// Returns the number of deleted documents.
+    pub fn num_deleted_docs(&self) -> u32 {
+        self.deletes
+            .as_ref()
+            .map(|delete_meta| delete_meta.num_deleted_docs)
+            .unwrap_or(0u32)
+    }
+
+    /// Returns the list of files that
+    /// are required for the segment meta.
+    ///
+    /// This is useful as the way tantivy removes files
+    /// is by removing all files that have been created by tantivy
+    /// and are not used by any segment anymore.
+    pub fn list_files(&self) -> HashSet {
+        SegmentComponent::iterator()
+            .map(|component| {
+                self.relative_path(*component)
+            })
+            .collect::>()
+        
+    }
+
+    /// Returns the relative path of a component of our segment.
+    ///  
+    /// It just joins the segment id with the extension 
+    /// associated to a segment component.
+    pub fn relative_path(&self, component: SegmentComponent) -> PathBuf {
+        let mut path = self.id().uuid_string();
+        path.push_str(&*match component {
+            SegmentComponent::POSITIONS => ".pos".to_string(),
+            SegmentComponent::POSTINGS => ".idx".to_string(),
+            SegmentComponent::TERMS => ".term".to_string(),
+            SegmentComponent::STORE => ".store".to_string(),
+            SegmentComponent::FASTFIELDS => ".fast".to_string(),
+            SegmentComponent::FIELDNORMS => ".fieldnorm".to_string(),
+            SegmentComponent::DELETE => {format!(".{}.del", self.delete_opstamp().unwrap_or(0))},
+        });
+        PathBuf::from(path)
+    }
+
+    /// Return the highest doc id + 1
+    ///
+    /// If there are no deletes, then num_docs = max_docs
+    /// and all the doc ids contains in this segment
+    /// are exactly (0..max_doc).
+    pub fn max_doc(&self) -> u32 {
+        self.max_doc
+    }
+
+    /// Return the number of documents in the segment.
+    pub fn num_docs(&self) -> u32 {
+        self.max_doc() - self.num_deleted_docs()
+    }
+
+    /// Returns the opstamp of the last delete operation
+    /// taken in account in this segment.
+    pub fn delete_opstamp(&self) -> Option {
+        self.deletes
+            .as_ref()
+            .map(|delete_meta| delete_meta.opstamp)
+    }
+
+    /// Returns true iff the segment meta contains
+    /// delete information.
+    pub fn has_deletes(&self) -> bool {
+        self.deletes.is_some()
+    }
+
+    #[doc(hidden)]
+    pub fn set_max_doc(&mut self, max_doc: u32) {
+        self.max_doc = max_doc;
+    }
+
+    #[doc(hidden)]
+    pub fn set_delete_meta(&mut self, num_deleted_docs: u32, opstamp: u64) {
+        self.deletes = Some(DeleteMeta {
+            num_deleted_docs: num_deleted_docs,
+            opstamp: opstamp,
+        });
+    }
+}
diff --git a/src/core/segment_reader.rs b/src/core/segment_reader.rs
index f765c982e..7a3325730 100644
--- a/src/core/segment_reader.rs
+++ b/src/core/segment_reader.rs
@@ -3,17 +3,18 @@ use core::Segment;
 use core::SegmentId;
 use core::SegmentComponent;
 use schema::Term;
+use common::HasLen;
+use core::SegmentMeta;
+use fastfield::delete::DeleteBitSet;
 use store::StoreReader;
 use schema::Document;
 use directory::ReadOnlySource;
 use DocId;
-use std::io;
 use std::str;
 use postings::TermInfo;
 use datastruct::TermDictionary;
+use std::sync::Arc;
 use std::fmt;
-use rustc_serialize::json;
-use core::SegmentInfo;
 use schema::Field;
 use postings::{SegmentPostings, BlockSegmentPostings, SegmentPostingsOption};
 use fastfield::{U32FastFieldsReader, U32FastFieldReader};
@@ -21,8 +22,6 @@ use schema::Schema;
 use schema::FieldType;
 use postings::FreqHandler;
 use schema::TextIndexingOptions;
-use error::Error;
-
 
 /// Entry point to access all of the datastructures of the `Segment`
 ///
@@ -35,14 +34,16 @@ use error::Error;
 /// The segment reader has a very low memory footprint,
 /// as close to all of the memory data is mmapped.
 ///
+#[derive(Clone)]
 pub struct SegmentReader {
-    segment_info: SegmentInfo,
     segment_id: SegmentId,
-    term_infos: TermDictionary,
+    segment_meta: SegmentMeta,
+    term_infos: Arc>,
     postings_data: ReadOnlySource,
     store_reader: StoreReader,
-    fast_fields_reader: U32FastFieldsReader,
-    fieldnorms_reader: U32FastFieldsReader,
+    fast_fields_reader: Arc,
+    fieldnorms_reader: Arc,
+    delete_bitset: DeleteBitSet,
     positions_data: ReadOnlySource,
     schema: Schema,
 }
@@ -53,7 +54,7 @@ impl SegmentReader {
     /// Today, `tantivy` does not handle deletes, so it happens
     /// to also be the number of documents in the index.
     pub fn max_doc(&self) -> DocId {
-        self.segment_info.max_doc
+        self.segment_meta.max_doc()
     }
     
 
@@ -67,20 +68,39 @@ impl SegmentReader {
     /// Today, `tantivy` does not handle deletes so max doc and
     /// num_docs are the same.
     pub fn num_docs(&self) -> DocId {
-        self.segment_info.max_doc
+        self.segment_meta.num_docs()
     }
     
+    /// Return the number of documents that have been
+    /// deleted in the segment.
+    pub fn num_deleted_docs(&self) -> DocId {
+        self.delete_bitset.len() as DocId
+    }
+
     /// Accessor to a segment's fast field reader given a field.
-    pub fn get_fast_field_reader(&self, field: Field) -> io::Result {
+    pub fn get_fast_field_reader(&self, field: Field) -> Option {
+        /// Returns the u32 fast value reader if the field
+        /// is a u32 field indexed as "fast".
+        ///
+        /// Return None if the field is not a u32 field
+        /// indexed with the fast option.
+        ///
+        /// # Panics
+        /// May panic if the index is corrupted.
         let field_entry = self.schema.get_field_entry(field);
-        match *field_entry.field_type() {
-            FieldType::Str(_) => {
-                Err(io::Error::new(io::ErrorKind::Other, "fast field are not yet supported for text fields."))
+        match field_entry.field_type() {
+            &FieldType::Str(_) => {
+                warn!("Field <{}> is not a fast field. It is a text field, and fast text fields are not supported yet.", field_entry.name());
+                None
             },
-            FieldType::U32(_) => {
-                // TODO check that the schema allows that
-                //Err(io::Error::new(io::ErrorKind::Other, "fast field are not yet supported for text fields."))
-                self.fast_fields_reader.get_field(field)
+            &FieldType::U32(ref u32_options) => {
+                if u32_options.is_fast() {
+                    self.fast_fields_reader.get_field(field)
+                }
+                else {
+                    warn!("Field <{}> is not defined as a fast field.", field_entry.name());
+                    None
+                }
             },
         }
     }
@@ -92,7 +112,7 @@ impl SegmentReader {
     ///
     /// They are simply stored as a fast field, serialized in 
     /// the `.fieldnorm` file of the segment. 
-    pub fn get_fieldnorms_reader(&self, field: Field) -> io::Result {
+    pub fn get_fieldnorms_reader(&self, field: Field) -> Option {
         self.fieldnorms_reader.get_field(field) 
     }
         
@@ -111,21 +131,7 @@ impl SegmentReader {
 
     /// Open a new segment for reading.
     pub fn open(segment: Segment) -> Result {
-        let segment_info_reader = try!(segment.open_read(SegmentComponent::INFO));
-        let segment_info_data = try!(
-            str::from_utf8(&*segment_info_reader)
-                .map_err(|err| {
-                    let segment_info_filepath = segment.relative_path(SegmentComponent::INFO);
-                    Error::CorruptedFile(segment_info_filepath, Box::new(err))
-                })
-         );
-        let segment_info: SegmentInfo = try!(
-            json::decode(&segment_info_data)
-            .map_err(|err| {
-                let file_path = segment.relative_path(SegmentComponent::INFO);
-                Error::CorruptedFile(file_path, Box::new(err))
-            })
-        );
+
         let source = try!(segment.open_read(SegmentComponent::TERMS));
         let term_infos = try!(TermDictionary::from_source(source));
         let store_reader = StoreReader::from(try!(segment.open_read(SegmentComponent::STORE)));
@@ -141,15 +147,25 @@ impl SegmentReader {
             .open_read(SegmentComponent::POSITIONS)
             .unwrap_or_else(|_| ReadOnlySource::empty());
         
+        let delete_bitset =
+            if segment.meta().has_deletes() {
+                let delete_data = segment.open_read(SegmentComponent::DELETE)?;
+                DeleteBitSet::open(delete_data)
+            }
+            else {
+                DeleteBitSet::empty()
+            };
+        
         let schema = segment.schema();
         Ok(SegmentReader {
-            segment_info: segment_info,
+            segment_meta: segment.meta().clone(),
             postings_data: postings_shared_mmap,
-            term_infos: term_infos,
+            term_infos: Arc::new(term_infos),
             segment_id: segment.id(),
             store_reader: store_reader,
-            fast_fields_reader: fast_fields_reader,
-            fieldnorms_reader: fieldnorms_reader,
+            fast_fields_reader: Arc::new(fast_fields_reader),
+            fieldnorms_reader: Arc::new(fieldnorms_reader),
+            delete_bitset: delete_bitset,
             positions_data: positions_data,
             schema: schema,
         })
@@ -237,10 +253,17 @@ impl SegmentReader {
     /// that does not index position will return a `SegmentPostings` with `DocId`s and frequencies.
     pub fn read_postings(&self, term: &Term, option: SegmentPostingsOption) -> Option {
         self.read_block_postings(term, option)
-            .map(SegmentPostings::from_block_postings)
+            .map(|block_postings| {
+                 SegmentPostings::from_block_postings(block_postings, self.delete_bitset.clone())
+            })
     }
-        
+    
+
     /// Returns the posting list associated with a term.
+    ///
+    /// If the term is not found, return None.
+    /// Even when non-null, because of deletes, the posting object 
+    /// returned by this method may contain no documents.
     pub fn read_postings_all_info(&self, term: &Term) -> Option {
         let field_entry = self.schema.get_field_entry(term.field());
         let segment_posting_option = match *field_entry.field_type() {
@@ -260,6 +283,24 @@ impl SegmentReader {
     pub fn get_term_info(&self, term: &Term) -> Option {
         self.term_infos.get(term.as_slice())
     }
+
+    /// Returns the segment id
+    pub fn segment_id(&self) -> SegmentId {
+        self.segment_id
+    }
+
+    /// Returns the bitset representing
+    /// the documents that have been deleted.
+    pub fn delete_bitset(&self) -> &DeleteBitSet {
+        &self.delete_bitset
+    }
+
+
+    /// Returns true iff the `doc` is marked
+    /// as deleted.
+    pub fn is_deleted(&self, doc: DocId) -> bool {
+        self.delete_bitset.is_deleted(doc)
+    }
 }
 
 
diff --git a/src/core/term_iterator.rs b/src/core/term_iterator.rs
index dc39e5528..5ac68f929 100644
--- a/src/core/term_iterator.rs
+++ b/src/core/term_iterator.rs
@@ -101,7 +101,7 @@ impl<'a> TermIterator<'a> {
         for segment_ord in self.current_segment_ords.drain(..) {
             if let Some((term, val)) = self.key_streams[segment_ord].next() {
                 self.heap.push(HeapItem {
-                    term: Term::from(term),
+                    term: Term::from_bytes(term),
                     segment_ord: segment_ord,
                 });
             }
@@ -150,7 +150,7 @@ mod tests {
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "a b d f");
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 index_writer.commit().unwrap();
             }
@@ -158,7 +158,7 @@ mod tests {
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "a b c d f");
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 index_writer.commit().unwrap();
             }
@@ -166,11 +166,12 @@ mod tests {
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "e f");
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 index_writer.commit().unwrap();
             }
         }
+        index.load_searchers().unwrap();
         let searcher = index.searcher();
         let mut term_it = searcher.terms();
         let mut terms = String::new();
diff --git a/src/datastruct/fstmap.rs b/src/datastruct/fstmap.rs
index d4e5812ff..adaed1082 100644
--- a/src/datastruct/fstmap.rs
+++ b/src/datastruct/fstmap.rs
@@ -21,7 +21,7 @@ pub struct FstMapBuilder {
 }
 
 impl FstMapBuilder {
-
+    
     pub fn new(w: W) -> io::Result> {
         let fst_builder = try!(fst::MapBuilder::new(w).map_err(convert_fst_error));
         Ok(FstMapBuilder {
@@ -31,8 +31,28 @@ impl FstMapBuilder {
         })
     }
 
+    /// Horribly unsafe, nobody should ever do that... except me :)
+    /// 
+    /// If used, it must be used by systematically alternating calls
+    /// to insert_key and insert_value.
+    ///
+    /// TODO see if I can bend Rust typesystem to enforce that
+    /// in a nice way.
+    pub fn insert_key(&mut self, key: &[u8]) -> io::Result<()> {
+        try!(self.fst_builder
+            .insert(key, self.data.len() as u64)
+            .map_err(convert_fst_error));
+        Ok(())
+    }
 
-    pub fn insert(&mut self, key: &[u8], value: &V) -> io::Result<()>{
+    /// Horribly unsafe, nobody should ever do that... except me :)
+    pub fn insert_value(&mut self, value: &V) -> io::Result<()> {
+        try!(value.serialize(&mut self.data));
+        Ok(())
+    }
+
+    #[cfg(test)]
+    pub fn insert(&mut self, key: &[u8], value: &V) -> io::Result<()> {
         try!(self.fst_builder
             .insert(key, self.data.len() as u64)
             .map_err(convert_fst_error));
@@ -132,7 +152,6 @@ mod tests {
         assert_eq!(keys.next().unwrap(), "abc".as_bytes());
         assert_eq!(keys.next().unwrap(), "abcd".as_bytes());
         assert_eq!(keys.next(), None);
- 
     }
 
 }
diff --git a/src/datastruct/skip/skiplist_builder.rs b/src/datastruct/skip/skiplist_builder.rs
index b83406029..9806a69af 100644
--- a/src/datastruct/skip/skiplist_builder.rs
+++ b/src/datastruct/skip/skiplist_builder.rs
@@ -36,7 +36,7 @@ impl LayerBuilder {
     fn insert(&mut self, doc_id: DocId, value: &T) -> io::Result> {
         self.remaining -= 1;
         self.len += 1;
-        let offset = self.written_size() as u32; // TODO not sure if we want after or here
+        let offset = self.written_size() as u32;
         try!(doc_id.serialize(&mut self.buffer));
         try!(value.serialize(&mut self.buffer));
         Ok(if self.remaining == 0 {
diff --git a/src/datastruct/stacker/heap.rs b/src/datastruct/stacker/heap.rs
index 9a43de897..1ae116f2b 100644
--- a/src/datastruct/stacker/heap.rs
+++ b/src/datastruct/stacker/heap.rs
@@ -1,5 +1,6 @@
 use std::cell::UnsafeCell;
 use std::mem;
+use common::allocate_vec;
 use std::ptr;
 
 /// `BytesRef` refers to a slice in tantivy's custom `Heap`.
@@ -41,7 +42,6 @@ impl Heap {
         self.inner().clear();
     }
     
-    
     /// Return the heap capacity.
     pub fn capacity(&self,) -> u32 {
         self.inner().capacity()
@@ -91,6 +91,10 @@ impl Heap {
     pub fn get_mut_ref(&self, addr: u32) -> &mut Item {
         self.inner().get_mut_ref(addr)
     }
+
+    pub fn get_ref(&self, addr: u32) -> &Item {
+        self.inner().get_mut_ref(addr)
+    }
 }
 
 
@@ -101,22 +105,11 @@ struct InnerHeap {
     next_heap: Option>,
 }
 
-/// initializing a long Vec is crazy slow in 
-/// debug mode.
-/// We use this unsafe trick to make unit test
-/// way faster.
-fn allocate_fast(num_bytes: usize) -> Vec {
-    let mut buffer = Vec::with_capacity(num_bytes);
-    unsafe {
-        buffer.set_len(num_bytes);
-    }
-    buffer
-}
 
 impl InnerHeap {
 
     pub fn with_capacity(num_bytes: usize) -> InnerHeap {
-        let buffer: Vec = allocate_fast(num_bytes);
+        let buffer: Vec = allocate_vec(num_bytes);
         InnerHeap {
             buffer: buffer,
             buffer_len: num_bytes as u32,
diff --git a/src/datastruct/stream_dictionary.rs b/src/datastruct/stream_dictionary.rs
index 14b905835..a725b26c6 100644
--- a/src/datastruct/stream_dictionary.rs
+++ b/src/datastruct/stream_dictionary.rs
@@ -122,6 +122,11 @@ impl StreamDictionaryBuilder<
     }
 
     pub fn insert(&mut self, key: &[u8], value: &V) -> io::Result<()>{
+        self.insert_key(key)?;
+        self.insert_value(value)
+    }
+
+    pub fn insert_key(&mut self, key: &[u8]) -> io::Result<()>{
         if self.len % BLOCK_SIZE == 0 {
             self.add_index_entry();
         }
@@ -132,6 +137,10 @@ impl StreamDictionaryBuilder<
         self.last_key.extend_from_slice(&key[common_len..]);
         VInt((key.len() - common_len) as u64).serialize(&mut self.write)?;
         self.write.write_all(&key[common_len..])?;
+        Ok(())
+    }
+
+    pub fn insert_value(&mut self, value: &V) -> io::Result<()>{
         value.serialize(&mut self.write)?;
         Ok(())
     }
diff --git a/src/directory/directory.rs b/src/directory/directory.rs
index 6171ed606..b555efbcc 100644
--- a/src/directory/directory.rs
+++ b/src/directory/directory.rs
@@ -1,13 +1,14 @@
 use std::marker::Send;
 use std::fmt;
 use std::path::Path;
-use directory::error::{FileError, OpenWriteError};
+use directory::error::{OpenReadError, DeleteError, OpenWriteError};
 use directory::{ReadOnlySource, WritePtr};
 use std::result;
 use std::io;
 use std::marker::Sync;
 
-/// Write-once read many (WORM) abstraction for where tantivy's index should be stored. 
+/// Write-once read many (WORM) abstraction for where
+/// tantivy's data should be stored. 
 ///
 /// There are currently two implementations of `Directory`
 /// 
@@ -25,16 +26,16 @@ pub trait Directory: fmt::Debug + Send + Sync + 'static {
     ///
     /// Specifically, subsequent writes or flushes should
     /// have no effect on the returned `ReadOnlySource` object. 
-    fn open_read(&self, path: &Path) -> result::Result;
-    
+    fn open_read(&self, path: &Path) -> result::Result;
+
     /// Removes a file
     ///
     /// Removing a file will not affect an eventual
     /// existing ReadOnlySource pointing to it.
     /// 
     /// Removing a nonexistent file, yields a
-    /// `FileError::DoesNotExist`.
-    fn delete(&self, path: &Path) -> result::Result<(), FileError>;
+    /// `DeleteError::DoesNotExist`.
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError>;
 
     /// Returns true iff the file exists
     fn exists(&self, path: &Path) -> bool;
@@ -60,6 +61,12 @@ pub trait Directory: fmt::Debug + Send + Sync + 'static {
     /// The file may not previously exist.
     fn open_write(&mut self, path: &Path) -> Result;
     
+    /// Reads the full content file that has been written using
+    /// atomic_write.
+    ///
+    /// This should only be used for small files.
+    fn atomic_read(&self, path: &Path) -> Result, OpenReadError>;
+
     /// Atomically replace the content of a file with data.
     /// 
     /// This calls ensure that reads can never *observe*
@@ -70,6 +77,7 @@ pub trait Directory: fmt::Debug + Send + Sync + 'static {
         
     /// Clones the directory and boxes the clone 
     fn box_clone(&self) -> Box;
+
 }
 
 
diff --git a/src/directory/error.rs b/src/directory/error.rs
index a49ea23b7..b2a7f24f1 100644
--- a/src/directory/error.rs
+++ b/src/directory/error.rs
@@ -27,9 +27,9 @@ impl From for OpenWriteError {
     }
 }
 
-/// Error that may occur when accessing a file (read, or delete)
+/// Error that may occur when accessing a file read
 #[derive(Debug)]
-pub enum FileError {
+pub enum OpenReadError {
     /// The file does not exists.
     FileDoesNotExist(PathBuf),
     /// Any kind of IO error that happens when 
@@ -37,8 +37,16 @@ pub enum FileError {
     IOError(io::Error),
 }
 
-impl From for FileError {
-    fn from(err: io::Error) -> FileError {
-        FileError::IOError(err)
-    }
+
+/// Error that may occur when trying to delete a file
+#[derive(Debug)]
+pub enum DeleteError {
+    /// The file does not exists.
+    FileDoesNotExist(PathBuf),
+    /// Any kind of IO error that happens when 
+    /// interacting with the underlying IO device.
+    IOError(io::Error),
+    /// The file may not be deleted because it is 
+    /// protected.
+    FileProtected(PathBuf),
 }
diff --git a/src/directory/managed_directory.rs b/src/directory/managed_directory.rs
new file mode 100644
index 000000000..49c41fa49
--- /dev/null
+++ b/src/directory/managed_directory.rs
@@ -0,0 +1,405 @@
+use std::path::{Path, PathBuf};
+use directory::error::{OpenReadError, DeleteError, OpenWriteError};
+use directory::{ReadOnlySource, WritePtr};
+use std::result;
+use std::io;
+use Directory;
+use std::sync::{Arc, RwLock};
+use std::collections::HashSet;
+use std::io::Write;
+use rustc_serialize::json;
+use core::MANAGED_FILEPATH;
+use std::collections::HashMap;
+use std::fmt;
+use Result;
+use Error;
+
+/// Wrapper of directories that keeps track of files created by Tantivy.
+///
+/// A managed directory is just a wrapper of a directory
+/// that keeps a (persisted) list of the files that 
+/// have been created (and not deleted) by tantivy so far.
+///
+/// Thanks to this list, it implements a `garbage_collect` method
+/// that removes the files that were created by tantivy and are not
+/// useful anymore.
+#[derive(Debug)]
+pub struct ManagedDirectory {
+    directory: Box,
+    meta_informations: Arc>,
+}
+
+#[derive(Debug, Default)]
+struct MetaInformation {
+    managed_paths: HashSet,
+    protected_files: HashMap,
+}
+
+
+/// A `FileProtection` prevents the garbage collection of a file.
+///
+/// See `ManagedDirectory.protect_file_from_delete`.
+pub struct FileProtection {
+    directory: ManagedDirectory,
+    path: PathBuf,
+}
+
+fn unprotect_file_from_delete(directory: &ManagedDirectory, path: &Path) {
+    let mut meta_informations_wlock = directory.meta_informations
+        .write()
+        .expect("Managed file lock poisoned");
+    if let Some(counter_ref_mut) = meta_informations_wlock
+        .protected_files
+        .get_mut(path) {
+        (*counter_ref_mut) -= 1;
+    }
+}
+
+impl fmt::Debug for FileProtection {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> result::Result<(), fmt::Error> {
+        write!(formatter, "FileProtectionFor({:?})", self.path)    
+    }
+}
+
+impl Drop for FileProtection {
+    fn drop(&mut self) {
+        unprotect_file_from_delete(&self.directory, &*self.path);
+    }
+}
+
+impl ManagedDirectory {
+
+    /// Wraps a directory as managed directory.
+    pub fn new(directory: Dir) -> Result {
+        match directory.atomic_read(&MANAGED_FILEPATH) {
+            Ok(data) => {
+                let managed_files_json = String::from_utf8_lossy(&data);
+                let managed_files: HashSet = json::decode(&managed_files_json)
+                    .map_err(|e| Error::CorruptedFile(MANAGED_FILEPATH.clone(), Box::new(e)))?;
+                Ok(ManagedDirectory {
+                    directory: box directory,
+                    meta_informations: Arc::new(RwLock::new(
+                        MetaInformation {
+                            managed_paths: managed_files,
+                            protected_files: HashMap::default()
+                        })),
+                })
+            }
+            Err(OpenReadError::FileDoesNotExist(_)) => {
+                Ok(ManagedDirectory {
+                    directory: box directory,
+                    meta_informations: Arc::default(),
+                })
+            }
+            Err(OpenReadError::IOError(e)) => {
+                Err(From::from(e))
+            }
+        }
+    }
+
+    /// Garbage collect unused files.
+    ///
+    /// Removes the files that were created by `tantivy` and are not
+    /// used by any segment anymore.
+    /// 
+    /// * `living_files` - List of files that are still used by the index.
+    ///
+    /// This method does not panick nor returns errors.
+    /// If a file cannot be deleted (for permission reasons for instance)
+    /// an error is simply logged, and the file remains in the list of managed
+    /// files.
+    pub fn garbage_collect(&mut self, living_files: HashSet) {
+        let mut files_to_delete = vec!();
+        {   // releasing the lock as .delete() will use it too.
+            let meta_informations_rlock = self.meta_informations
+                .read()
+                .expect("Managed directory rlock poisoned in garbage collect.");
+            for managed_path in &meta_informations_rlock.managed_paths {
+                if !living_files.contains(managed_path) {
+                    files_to_delete.push(managed_path.clone());
+                }
+            }
+        }
+        
+        let mut deleted_files = vec!();
+        {
+            for file_to_delete in files_to_delete {
+                match self.delete(&file_to_delete) {
+                    Ok(_) => {
+                        info!("Deleted {:?}", file_to_delete);
+                        deleted_files.push(file_to_delete);
+                    }
+                    Err(file_error) => {
+                        error!("Failed to delete {:?}", file_to_delete);
+                        match file_error {
+                            DeleteError::FileDoesNotExist(_) => {
+                                deleted_files.push(file_to_delete);
+                            }
+                            DeleteError::IOError(_) => {
+                                if !cfg!(target_os = "windows") {
+                                    error!("Failed to delete {:?}", file_to_delete);
+                                }
+                            }
+                            DeleteError::FileProtected(_) => {
+                                // this is expected.
+                            }
+                        }
+                        
+                    }
+                }
+            }
+        }
+
+
+        if !deleted_files.is_empty() {
+            // update the list of managed files by removing 
+            // the file that were removed.
+            {
+                let mut meta_informations_wlock = self.meta_informations
+                    .write()
+                    .expect("Managed directory wlock poisoned (2).");
+                let managed_paths_write = &mut meta_informations_wlock.managed_paths;
+                for delete_file in &deleted_files {
+                    managed_paths_write.remove(delete_file);
+                }
+            }
+            if let Err(_) = self.save_managed_paths() {
+                error!("Failed to save the list of managed files.");
+            }
+        }
+
+    }
+
+
+    /// Protects a file from being garbage collected.
+    ///
+    /// The method returns a `FileProtection` object.
+    /// The file will not be garbage collected as long as the
+    /// `FileProtection` object is kept alive. 
+    pub fn protect_file_from_delete(&self, path: &Path) -> FileProtection {
+        let pathbuf = path.to_owned();
+        {
+            let mut meta_informations_wlock = self.meta_informations
+                .write()
+                .expect("Managed file lock poisoned on protect");
+            *meta_informations_wlock
+                .protected_files
+                .entry(pathbuf.clone())
+                .or_insert(0) += 1;
+        }
+        FileProtection {
+            directory: self.clone(),
+            path: pathbuf.clone(),
+        }
+    }
+
+
+    /// Saves the file containing the list of existing files
+    /// that were created by tantivy.
+    fn save_managed_paths(&mut self,) -> io::Result<()> {
+        let managed_paths;
+        {
+            let meta_informations_rlock = self.meta_informations
+                .read()
+                .expect("Managed file lock poisoned");
+            managed_paths = meta_informations_rlock.managed_paths.clone();
+        }
+        let mut w = vec!();
+        try!(write!(&mut w, "{}\n", json::as_pretty_json(&managed_paths)));
+        self.directory.atomic_write(&MANAGED_FILEPATH, &w[..])?;
+        Ok(())
+    }
+
+    /// Registers a file as managed
+    /// 
+    /// This method must be called before the file is 
+    /// actually created to ensure that a failure between
+    /// registering the filepath and creating the file
+    /// will not lead to garbage files that will 
+    /// never get removed.
+    fn register_file_as_managed(&mut self, filepath: &Path) -> io::Result<()> {
+        let has_changed = {
+            let mut meta_wlock = self.meta_informations
+                .write()
+                .expect("Managed file lock poisoned");
+            meta_wlock.managed_paths.insert(filepath.to_owned())
+        };
+        if has_changed {
+            self.save_managed_paths()?;
+        }
+        Ok(())
+    }
+}
+
+impl Directory for ManagedDirectory {
+    
+    fn open_read(&self, path: &Path) -> result::Result {
+        self.directory.open_read(path)
+    }
+
+    fn open_write(&mut self, path: &Path) -> result::Result {
+        self.register_file_as_managed(path)?;
+        self.directory.open_write(path)
+    }
+
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
+        self.register_file_as_managed(path)?;
+        self.directory.atomic_write(path, data)
+    }
+
+    fn atomic_read(&self, path: &Path) -> result::Result, OpenReadError> {
+        self.directory.atomic_read(path)
+    }
+
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
+        {
+            let metas_rlock = self.meta_informations
+                .read()
+                .expect("poisoned lock in managed directory meta");
+            if let Some(counter) = metas_rlock.protected_files.get(path) {
+                if *counter > 0 {
+                    return Err(DeleteError::FileProtected(path.to_owned()))
+                }
+            }
+        }
+        self.directory.delete(path)
+    }
+
+    fn exists(&self, path: &Path) -> bool {
+        self.directory.exists(path)
+    }
+    
+    fn box_clone(&self) -> Box {
+        box self.clone()
+    }
+
+}
+
+impl Clone for ManagedDirectory {
+    fn clone(&self) -> ManagedDirectory {
+        ManagedDirectory {
+            directory: self.directory.box_clone(),
+            meta_informations: self.meta_informations.clone(),
+        }
+    }
+}
+
+
+
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    use directory::MmapDirectory;
+    use std::path::Path;   
+    use std::io::Write;
+    use tempdir::TempDir;
+    
+    lazy_static! {
+        static ref TEST_PATH1: &'static Path = Path::new("some_path_for_test");
+        static ref TEST_PATH2: &'static Path = Path::new("some_path_for_test2");
+    }
+
+    #[test]
+    fn test_managed_directory() {
+        let tempdir = TempDir::new("index").unwrap();
+        let tempdir_path = PathBuf::from(tempdir.path());
+        {
+            let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
+            let mut managed_directory = ManagedDirectory::new(mmap_directory).unwrap();
+            {
+                let mut write_file = managed_directory.open_write(*TEST_PATH1).unwrap();
+                write_file.flush().unwrap();
+            }
+            {
+                managed_directory.atomic_write(*TEST_PATH2, &vec!(0u8,1u8)).unwrap();
+            }
+            {
+                assert!(managed_directory.exists(*TEST_PATH1));
+                assert!(managed_directory.exists(*TEST_PATH2));
+            }
+            {
+                let living_files: HashSet = [TEST_PATH1.to_owned()]
+                    .into_iter()
+                    .cloned()
+                    .collect();
+                managed_directory.garbage_collect(living_files);
+            }
+            {
+                assert!(managed_directory.exists(*TEST_PATH1));
+                assert!(!managed_directory.exists(*TEST_PATH2));
+            }
+        }
+        {
+            let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
+            let mut managed_directory = ManagedDirectory::new(mmap_directory).unwrap();
+            {
+                assert!(managed_directory.exists(*TEST_PATH1));
+                assert!(!managed_directory.exists(*TEST_PATH2));
+            }
+            {
+                let living_files: HashSet = HashSet::new();
+                managed_directory.garbage_collect(living_files);
+            }
+            {
+                assert!(!managed_directory.exists(*TEST_PATH1));
+                assert!(!managed_directory.exists(*TEST_PATH2));
+            }
+        }   
+    }
+
+    #[test]
+    fn test_managed_directory_gc_while_mmapped() {
+        let tempdir = TempDir::new("index").unwrap();
+        let tempdir_path = PathBuf::from(tempdir.path());
+        let living_files = HashSet::new();
+
+        let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
+        let mut managed_directory = ManagedDirectory::new(mmap_directory).unwrap();
+        managed_directory.atomic_write(*TEST_PATH1, &vec!(0u8,1u8)).unwrap();
+        assert!(managed_directory.exists(*TEST_PATH1));
+
+        let _mmap_read = managed_directory.open_read(*TEST_PATH1).unwrap();            
+        managed_directory.garbage_collect(living_files.clone());
+        if cfg!(target_os = "windows") {
+            // On Windows, gc should try and fail the file as it is mmapped.
+            assert!(managed_directory.exists(*TEST_PATH1));
+            // unmap should happen here.
+            drop(_mmap_read);
+            // The file should still be in the list of managed file and
+            // eventually be deleted once mmap is released.
+            managed_directory.garbage_collect(living_files);
+            assert!(!managed_directory.exists(*TEST_PATH1));
+        }
+        else {
+            assert!(!managed_directory.exists(*TEST_PATH1));
+        }
+
+    }
+
+
+    #[test]
+    fn test_managed_directory_protect() {
+        let tempdir = TempDir::new("index").unwrap();
+        let tempdir_path = PathBuf::from(tempdir.path());
+        let living_files = HashSet::new();
+
+        let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
+        let mut managed_directory = ManagedDirectory::new(mmap_directory).unwrap();
+        managed_directory.atomic_write(*TEST_PATH1, &vec!(0u8,1u8)).unwrap();
+        assert!(managed_directory.exists(*TEST_PATH1));
+
+        {
+            let _file_protection = managed_directory.protect_file_from_delete(*TEST_PATH1);
+            managed_directory.garbage_collect(living_files.clone());
+            assert!(managed_directory.exists(*TEST_PATH1));
+        }
+
+        managed_directory.garbage_collect(living_files.clone());
+        assert!(!managed_directory.exists(*TEST_PATH1));
+        
+
+    }
+
+}
diff --git a/src/directory/mmap_directory.rs b/src/directory/mmap_directory.rs
index 781f42e22..2437ceb35 100644
--- a/src/directory/mmap_directory.rs
+++ b/src/directory/mmap_directory.rs
@@ -1,7 +1,7 @@
 use atomicwrites;
 use common::make_io_err;
 use directory::Directory;
-use directory::error::{OpenWriteError, FileError, OpenDirectoryError};
+use directory::error::{OpenWriteError, OpenReadError, DeleteError, OpenDirectoryError};
 use directory::ReadOnlySource;
 use directory::shared_vec_slice::SharedVecSlice;
 use directory::WritePtr;
@@ -9,16 +9,13 @@ use fst::raw::MmapReadOnly;
 use memmap::{Mmap, Protection};
 use std::collections::hash_map::Entry as HashMapEntry;
 use std::collections::HashMap;
-use std::mem;
 use std::convert::From;
 use std::fmt;
-use std::fs;
-use std::fs::File;
+use std::fs::{self, File};
 use std::fs::OpenOptions;
-use std::io;
-use std::io::{Seek, SeekFrom};
-use std::io::BufWriter;
-use std::io::Write;
+use std::io::{self, Seek, SeekFrom};
+use std::io::{BufWriter, Read, Write};
+use std::mem;
 use std::path::{Path, PathBuf};
 use std::result;
 use std::sync::Arc;
@@ -26,31 +23,46 @@ use std::sync::RwLock;
 use std::sync::Weak;
 use tempdir::TempDir;
 
-
-fn open_mmap(full_path: &PathBuf) -> result::Result>, FileError> {
+fn open_mmap(full_path: &PathBuf) -> result::Result>, OpenReadError> {
     let convert_file_error = |err: io::Error| {
         if err.kind() == io::ErrorKind::NotFound {
-            FileError::FileDoesNotExist(full_path.clone())
+            OpenReadError::FileDoesNotExist(full_path.clone())
         }
         else {
-            FileError::IOError(err)
+            OpenReadError::IOError(err)
         }
     };
     let file = File::open(&full_path).map_err(convert_file_error)?;
-    if try!(file.metadata()).len() == 0 {
+    let meta_data = file
+        .metadata()
+        .map_err(|e| OpenReadError::IOError(e))?;
+    if meta_data.len() == 0 {
         // if the file size is 0, it will not be possible 
         // to mmap the file, so we return an anonymous mmap_cache
         // instead.
         return Ok(None)
     }
-    Ok(Some(Arc::new(Mmap::open(&file, Protection::Read)?)))
+    match Mmap::open(&file, Protection::Read) {
+        Ok(mmap) => {
+            Ok(Some(Arc::new(mmap)))
+        }
+        Err(e) => {
+            Err(OpenReadError::IOError(e))
+        }
+    }
+    
 }
 
 #[derive(Default,Clone,Debug,RustcDecodable,RustcEncodable)]
 pub struct CacheCounters {
-    hit: usize,
-    miss_empty: usize,
-    miss_weak: usize,
+    // Number of time the cache prevents to call `mmap`
+    pub hit: usize,
+    // Number of time tantivy had to call `mmap`
+    // as no entry was in the cache.
+    pub miss_empty: usize,
+    // Number of time tantivy had to call `mmap`
+    // as the entry in the cache was evinced.
+    pub miss_weak: usize,
 }
 
 #[derive(Clone,Debug,RustcDecodable,RustcEncodable)]
@@ -104,7 +116,7 @@ impl MmapCache {
         }
     }
 
-    fn get_mmap(&mut self, full_path: PathBuf) -> Result>, FileError> {
+    fn get_mmap(&mut self, full_path: PathBuf) -> Result>, OpenReadError> {
         // if we exceed this limit, then we go through the weak
         // and remove those that are obsolete.
         if self.cache.len() > self.purge_weak_limit {
@@ -206,12 +218,33 @@ impl MmapDirectory {
     /// Sync the root directory.
     /// In certain FS, this is required to persistently create
     /// a file.
-    fn sync_directory(&self,) -> Result<(), io::Error> {
-        let fd = try!(File::open(&self.root_path));
+    fn sync_directory(&self) -> Result<(), io::Error> {
+        let mut open_opts = OpenOptions::new();
+
+        // Linux needs read to be set, otherwise returns EINVAL
+        // write must not be set, or it fails with EISDIR
+        open_opts.read(true);
+
+        // On Windows, opening a directory requires FILE_FLAG_BACKUP_SEMANTICS
+        // and calling sync_all() only works if write access is requested.
+        #[cfg(windows)]
+        {
+            use std::os::windows::fs::OpenOptionsExt;
+            use winapi::winbase;
+
+            open_opts.write(true)
+                .custom_flags(winbase::FILE_FLAG_BACKUP_SEMANTICS);
+        }
+
+        let fd = try!(open_opts.open(&self.root_path));
         try!(fd.sync_all());
         Ok(())
     }
-
+    /// Returns some statistical information
+    /// about the Mmap cache.
+    /// 
+    /// The `MmapDirectory` embeds a `MmapDirectory` 
+    /// to avoid multiplying the `mmap` system calls.
     pub fn get_cache_info(&mut self) -> CacheInfo {
         self.mmap_cache
             .write()
@@ -253,15 +286,15 @@ impl Seek for SafeFileWriter {
 
 impl Directory for MmapDirectory {
     
-    fn open_read(&self, path: &Path) -> result::Result {
+    fn open_read(&self, path: &Path) -> result::Result {
         debug!("Open Read {:?}", path);
         let full_path = self.resolve_path(path);
         
         let mut mmap_cache = self.mmap_cache
             .write()
-            .map_err(|_| {
+            .map_err(|_| OpenReadError::IOError(
                 make_io_err(format!("Failed to acquired write lock on mmap cache while reading {:?}", path))
-            })?;
+            ))?;
         
         Ok(mmap_cache.get_mmap(full_path)?
             .map(MmapReadOnly::from)
@@ -301,22 +334,32 @@ impl Directory for MmapDirectory {
         Ok(BufWriter::new(Box::new(writer)))
     }
 
-    fn delete(&self, path: &Path) -> result::Result<(), FileError> {
-        debug!("Delete {:?}", path);
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
+        debug!("Deleting file {:?}", path);
         let full_path = self.resolve_path(path);
         let mut mmap_cache = try!(self.mmap_cache
             .write()
-            .map_err(|_| {
-                make_io_err(format!("Failed to acquired write lock on mmap cache while deleting {:?}", path))
-            })
+            .map_err(|_| 
+                 DeleteError::IOError(make_io_err(format!("Failed to acquired write lock on mmap cache while deleting {:?}", path))))
         );
         // Removing the entry in the MMap cache.
         // The munmap will appear on Drop,
         // when the last reference is gone.
         mmap_cache.cache.remove(&full_path);
-        try!(fs::remove_file(&full_path));
-        try!(self.sync_directory());
-        Ok(())
+        match fs::remove_file(&full_path) {
+            Ok(_) => {
+                self.sync_directory()
+                    .map_err(|e| DeleteError::IOError(e))
+            }
+            Err(e) => {
+                if e.kind() == io::ErrorKind::NotFound {
+                    Err(DeleteError::FileDoesNotExist(path.to_owned()))
+                }
+                else {
+                    Err(DeleteError::IOError(e))
+                }
+            }
+        }
     }
 
     fn exists(&self, path: &Path) -> bool {
@@ -324,6 +367,27 @@ impl Directory for MmapDirectory {
         full_path.exists()
     }
 
+    fn atomic_read(&self, path: &Path) -> Result, OpenReadError> {
+        let full_path = self.resolve_path(path);
+        let mut buffer = Vec::new();
+        match File::open(&full_path) {
+            Ok(mut file) => {
+                file.read_to_end(&mut buffer)
+                    .map_err(|e| OpenReadError::IOError(e))?;
+                Ok(buffer)
+            }
+            Err(e) => {
+                if e.kind() == io::ErrorKind::NotFound {
+                    Err(OpenReadError::FileDoesNotExist(path.to_owned()))
+                }
+                else {
+                    Err(OpenReadError::IOError(e))
+                }
+            }
+        }
+        
+    }
+
     fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         debug!("Atomic Write {:?}", path);
         let full_path = self.resolve_path(path);
@@ -337,7 +401,6 @@ impl Directory for MmapDirectory {
     fn box_clone(&self,) -> Box {
         Box::new(self.clone())
     }
-    
 }
 
 
diff --git a/src/directory/mod.rs b/src/directory/mod.rs
index d6873ecc8..09f61da3e 100644
--- a/src/directory/mod.rs
+++ b/src/directory/mod.rs
@@ -3,6 +3,7 @@ mod ram_directory;
 mod directory;
 mod read_only_source;
 mod shared_vec_slice;
+mod managed_directory;
 
 /// Errors specific to the directory module.
 pub mod error;
@@ -14,6 +15,7 @@ pub use self::read_only_source::ReadOnlySource;
 pub use self::directory::Directory;
 pub use self::ram_directory::RAMDirectory;
 pub use self::mmap_directory::MmapDirectory;
+pub use self::managed_directory::{ManagedDirectory, FileProtection};
 
 /// Synonym of Seek + Write
 pub trait SeekableWrite: Seek + Write {}
@@ -58,31 +60,37 @@ mod tests {
 
     fn test_simple(directory: &mut Directory) {
         {
-            let mut write_file = directory.open_write(*TEST_PATH).unwrap();
-            assert!(directory.exists(*TEST_PATH));
-            write_file.write_all(&[4]).unwrap();
-            write_file.write_all(&[3]).unwrap();
-            write_file.write_all(&[7,3,5]).unwrap();
-            write_file.flush().unwrap();
+            {
+                let mut write_file = directory.open_write(*TEST_PATH).unwrap();
+                assert!(directory.exists(*TEST_PATH));
+                write_file.write_all(&[4]).unwrap();
+                write_file.write_all(&[3]).unwrap();
+                write_file.write_all(&[7,3,5]).unwrap();
+                write_file.flush().unwrap();
+            }
+            let read_file = directory.open_read(*TEST_PATH).unwrap();
+            let data: &[u8] = &*read_file;
+            assert_eq!(data, &[4u8, 3u8, 7u8, 3u8, 5u8]);
         }
-        let read_file = directory.open_read(*TEST_PATH).unwrap();
-        let data: &[u8] = &*read_file;
-        assert_eq!(data, &[4u8, 3u8, 7u8, 3u8, 5u8]);
+
         assert!(directory.delete(*TEST_PATH).is_ok());
         assert!(!directory.exists(*TEST_PATH));
     }
 
     fn test_seek(directory: &mut Directory) {
         {
-            let mut write_file = directory.open_write(*TEST_PATH).unwrap();
-            write_file.write_all(&[4, 3, 7,3,5]).unwrap();
-            write_file.seek(SeekFrom::Start(0)).unwrap();
-            write_file.write_all(&[3,1]).unwrap();
-            write_file.flush().unwrap();
+            {
+                let mut write_file = directory.open_write(*TEST_PATH).unwrap();
+                write_file.write_all(&[4, 3, 7,3,5]).unwrap();
+                write_file.seek(SeekFrom::Start(0)).unwrap();
+                write_file.write_all(&[3,1]).unwrap();
+                write_file.flush().unwrap();
+            }
+            let read_file = directory.open_read(*TEST_PATH).unwrap();
+            let data: &[u8] = &*read_file;
+            assert_eq!(data, &[3u8, 1u8, 7u8, 3u8, 5u8]);
         }
-        let read_file = directory.open_read(*TEST_PATH).unwrap();
-        let data: &[u8] = &*read_file;
-        assert_eq!(data, &[3u8, 1u8, 7u8, 3u8, 5u8]);
+
         assert!(directory.delete(*TEST_PATH).is_ok());
     }
 
@@ -111,19 +119,32 @@ mod tests {
         }
     }
 
-    fn test_delete(directory: &mut Directory) {
+    fn test_directory_delete(directory: &mut Directory) {
         assert!(directory.open_read(*TEST_PATH).is_err());
         let mut write_file = directory.open_write(*TEST_PATH).unwrap();
         write_file.write_all(&[1, 2, 3, 4]).unwrap();
         write_file.flush().unwrap();
-        let read_handle = directory.open_read(*TEST_PATH).unwrap();  
         {
-            assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
-            assert!(directory.delete(*TEST_PATH).is_ok());
-            assert!(directory.delete(Path::new("SomeOtherPath")).is_err());
-            assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
+            let read_handle = directory.open_read(*TEST_PATH).unwrap();
+            {
+                assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
+
+                // Mapped files can't be deleted on Windows
+                if !cfg!(windows) {
+                    assert!(directory.delete(*TEST_PATH).is_ok());
+                    assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
+                }
+
+                assert!(directory.delete(Path::new("SomeOtherPath")).is_err());
+            }
         }
+
+        if cfg!(windows) {
+            assert!(directory.delete(*TEST_PATH).is_ok());
+        }
+
         assert!(directory.open_read(*TEST_PATH).is_err());
+        assert!(directory.delete(*TEST_PATH).is_err());
     }
 
     fn test_directory(directory: &mut Directory) {
@@ -131,7 +152,7 @@ mod tests {
         test_seek(directory);
         test_rewrite_forbidden(directory);
         test_write_create_the_file(directory);
-        test_delete(directory);
+        test_directory_delete(directory);
     }
 
 }
diff --git a/src/directory/ram_directory.rs b/src/directory/ram_directory.rs
index 6ced0ae7e..ddb97080b 100644
--- a/src/directory/ram_directory.rs
+++ b/src/directory/ram_directory.rs
@@ -6,7 +6,7 @@ use std::result;
 use std::sync::{Arc, RwLock};
 use common::make_io_err;
 use directory::{Directory, ReadOnlySource};
-use directory::error::{OpenWriteError, FileError};
+use directory::error::{OpenWriteError, OpenReadError, DeleteError};
 use directory::WritePtr;
 use super::shared_vec_slice::SharedVecSlice;
 
@@ -55,7 +55,7 @@ impl Seek for VecWriter {
 impl Write for VecWriter {
     fn write(&mut self, buf: &[u8]) -> io::Result {
         self.is_flushed = false;
-        try!(self.data.write(buf));
+        try!(self.data.write_all(buf));
         Ok(buf.len())
     }
 
@@ -87,29 +87,29 @@ impl InnerDirectory {
         Ok(prev_value.is_some())
     }
 
-    fn open_read(&self, path: &Path) -> Result { 
+    fn open_read(&self, path: &Path) -> Result { 
         self.0
             .read()
             .map_err(|_| {
                 let io_err = make_io_err(format!("Failed to acquire read lock for the directory, when trying to read {:?}", path));
-                FileError::IOError(io_err)
+                OpenReadError::IOError(io_err)
             })
             .and_then(|readable_map| {
                 readable_map
                 .get(path)
-                .ok_or_else(|| FileError::FileDoesNotExist(PathBuf::from(path)))
+                .ok_or_else(|| OpenReadError::FileDoesNotExist(PathBuf::from(path)))
                 .map(|data| {
                     ReadOnlySource::Anonymous(SharedVecSlice::new(data.clone()))
                 })
             })
     }
 
-    fn delete(&self, path: &Path) -> result::Result<(), FileError> {
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
         self.0
             .write()
             .map_err(|_| {
                 let io_err = make_io_err(format!("Failed to acquire write lock for the directory, when trying to delete {:?}", path));
-                FileError::IOError(io_err)
+                DeleteError::IOError(io_err)
             })
             .and_then(|mut writable_map| {
                 match writable_map.remove(path) {
@@ -117,7 +117,7 @@ impl InnerDirectory {
                         Ok(())
                     },
                     None => {
-                        Err(FileError::FileDoesNotExist(PathBuf::from(path)))
+                        Err(DeleteError::FileDoesNotExist(PathBuf::from(path)))
                     }
                 }
             })
@@ -160,7 +160,7 @@ impl RAMDirectory {
 }
 
 impl Directory for RAMDirectory {
-    fn open_read(&self, path: &Path) -> result::Result {
+    fn open_read(&self, path: &Path) -> result::Result {
         self.fs.open_read(path)
     }
     
@@ -176,7 +176,7 @@ impl Directory for RAMDirectory {
         }
     }
 
-    fn delete(&self, path: &Path) -> result::Result<(), FileError> {
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
         self.fs.delete(path)
     }
 
@@ -185,6 +185,12 @@ impl Directory for RAMDirectory {
         self.fs.exists(path)
     }
 
+    fn atomic_read(&self, path: &Path) -> Result, OpenReadError> {
+        let read = self.open_read(path)?;
+        Ok(read.as_slice()
+               .to_owned())
+    }
+
     fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         let path_buf = PathBuf::from(path);
         let mut vec_writer = VecWriter::new(path_buf.clone(), self.fs.clone());
diff --git a/src/error.rs b/src/error.rs
index 6699c7134..5eaa50a9a 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -3,17 +3,16 @@
 /// Definition of Tantivy's error and result.
 
 use std::io;
-use std::result;
+
 use std::path::PathBuf;
 use std::error;
 use std::sync::PoisonError;
-use directory::error::{FileError, OpenWriteError, OpenDirectoryError};
+use directory::error::{OpenReadError, OpenWriteError, OpenDirectoryError};
 use query;
 use schema;
 
 
-/// Tantivy result.
-pub type Result = result::Result;
+
 
 
 /// Generic tantivy error.
@@ -32,11 +31,14 @@ pub enum Error {
     /// The data within is corrupted.
     ///
     /// For instance, it contains invalid JSON.
-    CorruptedFile(PathBuf, Box),
+    CorruptedFile(PathBuf, Box),
     /// Invalid argument was passed by the user.
     InvalidArgument(String),
     /// An Error happened in one of the thread
-    ErrorInThread(String), // TODO investigate better solution
+    ErrorInThread(String),
+    /// An Error appeared related to the lack of a field.
+    SchemaError(String),
+    
 }
 
 impl From for Error {
@@ -57,11 +59,11 @@ impl From> for Error {
     }
 }
 
-impl From for Error {
-    fn from(error: FileError) -> Error {
+impl From for Error {
+    fn from(error: OpenReadError) -> Error {
         match error {
-            FileError::FileDoesNotExist(filepath) => Error::PathDoesNotExist(filepath),
-            FileError::IOError(io_error) => Error::IOError(io_error),
+            OpenReadError::FileDoesNotExist(filepath) => Error::PathDoesNotExist(filepath),
+            OpenReadError::IOError(io_error) => Error::IOError(io_error),
         }
     }
 }
diff --git a/src/fastfield/delete.rs b/src/fastfield/delete.rs
new file mode 100644
index 000000000..83a631a38
--- /dev/null
+++ b/src/fastfield/delete.rs
@@ -0,0 +1,127 @@
+use bit_set::BitSet;
+use directory::WritePtr;
+use std::io::Write;
+use std::io;
+use directory::ReadOnlySource;
+use DocId;
+use common::HasLen;
+
+pub fn write_delete_bitset(delete_bitset: &BitSet, writer: &mut WritePtr) -> io::Result<()> {
+    let max_doc = delete_bitset.capacity();
+    let mut byte = 0u8;
+    let mut shift = 0u8;
+    for doc in 0..max_doc {
+        if delete_bitset.contains(doc) {
+            byte |= 1 << shift;
+        }
+        if shift == 7 {
+            writer.write_all(&[byte])?;
+            shift = 0;
+            byte = 0;
+        }
+        else {
+            shift += 1;
+        }
+    }
+    if max_doc % 8 > 0 {
+        writer.write_all(&[byte])?;
+    }
+    writer.flush()
+}
+
+#[derive(Clone)]
+pub struct DeleteBitSet {
+    data: ReadOnlySource,
+    len: usize,  
+}
+
+impl DeleteBitSet {
+
+    pub fn open(data: ReadOnlySource) -> DeleteBitSet {
+        let num_deleted: usize = data
+            .as_slice()
+            .iter()
+            .map(|b| b.count_ones() as usize)
+            .sum();
+        DeleteBitSet {
+            data: data,
+            len: num_deleted,
+        }
+    }
+
+    pub fn empty() -> DeleteBitSet {
+        DeleteBitSet {
+            data: ReadOnlySource::empty(),
+            len: 0,
+        }
+    }
+
+    pub fn has_deletes(&self) -> bool {
+        self.len() > 0
+    }
+
+    pub fn is_deleted(&self, doc: DocId) -> bool {
+        if self.len == 0 {
+            false
+        }
+        else {
+            let byte_offset = doc / 8u32;
+            let b: u8 = (*self.data)[byte_offset as usize];
+            let shift = (doc & 7u32) as u8;
+            b & (1u8 << shift) != 0    
+        }
+    }
+
+}
+
+
+impl HasLen for DeleteBitSet {
+    fn len(&self) -> usize {
+        self.len
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::PathBuf;
+    use bit_set::BitSet;
+    use directory::*;
+    use super::*;
+
+    fn test_delete_bitset_helper(bitset: &BitSet) {
+        let test_path = PathBuf::from("test");
+        let mut directory = RAMDirectory::create();
+        {
+            let mut writer = directory.open_write(&*test_path).unwrap();
+            write_delete_bitset(bitset, &mut writer).unwrap();
+        }
+        {
+            let source = directory.open_read(&test_path).unwrap();
+            let delete_bitset = DeleteBitSet::open(source);
+            let n = bitset.capacity();
+            for doc in 0..n {
+                assert_eq!(bitset.contains(doc), delete_bitset.is_deleted(doc as DocId));
+            }
+            assert_eq!(delete_bitset.len(), bitset.len());
+        }
+    }
+
+    #[test]
+    fn test_delete_bitset() {
+        {
+            let mut bitset = BitSet::with_capacity(10);
+            bitset.insert(1);
+            bitset.insert(9);
+            test_delete_bitset_helper(&bitset);
+        }
+        {
+            let mut bitset = BitSet::with_capacity(8);
+            bitset.insert(1);
+            bitset.insert(2);
+            bitset.insert(3);
+            bitset.insert(5);
+            bitset.insert(7);
+            test_delete_bitset_helper(&bitset);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/fastfield/mod.rs b/src/fastfield/mod.rs
index b51a5d15b..ae3d83f88 100644
--- a/src/fastfield/mod.rs
+++ b/src/fastfield/mod.rs
@@ -13,6 +13,7 @@
 mod reader;
 mod writer;
 mod serializer;
+pub mod delete;
 
 pub use self::writer::{U32FastFieldsWriter, U32FastFieldWriter};
 pub use self::reader::{U32FastFieldsReader, U32FastFieldReader};
@@ -53,9 +54,6 @@ mod tests {
     #[test]
     pub fn test_fastfield() {
         let test_fastfield = U32FastFieldReader::from(vec!(100,200,300));
-        println!("{}", test_fastfield.get(0));
-        println!("{}", test_fastfield.get(1));
-        println!("{}", test_fastfield.get(2));
         assert_eq!(test_fastfield.get(0), 100);
         assert_eq!(test_fastfield.get(1), 200);
         assert_eq!(test_fastfield.get(2), 300); 
diff --git a/src/fastfield/reader.rs b/src/fastfield/reader.rs
index 55be30059..2fd1a342a 100644
--- a/src/fastfield/reader.rs
+++ b/src/fastfield/reader.rs
@@ -32,7 +32,7 @@ pub struct U32FastFieldReader {
 impl U32FastFieldReader {
 
     pub fn empty() -> U32FastFieldReader {
-        U32FastFieldReader::open(U32_FAST_FIELD_EMPTY.clone()).expect("should always work.")
+        U32FastFieldReader::open(U32_FAST_FIELD_EMPTY.clone())
     }
 
     pub fn min_val(&self,) -> u32 {
@@ -43,14 +43,18 @@ impl U32FastFieldReader {
         self.max_val
     }
 
-    pub fn open(data: ReadOnlySource) -> io::Result {
+    /// Opens a new fast field reader given a read only source.
+    ///
+    /// # Panics
+    /// Panics if the data is corrupted.
+    pub fn open(data: ReadOnlySource) -> U32FastFieldReader {
         let min_val;
         let amplitude;
         let max_val;
         {
             let mut cursor = data.as_slice();
-            min_val = try!(u32::deserialize(&mut cursor));
-            amplitude = try!(u32::deserialize(&mut cursor));
+            min_val = u32::deserialize(&mut cursor).unwrap();
+            amplitude = u32::deserialize(&mut cursor).unwrap();
             max_val = min_val + amplitude;
         }
         let num_bits = compute_num_bits(amplitude);
@@ -58,12 +62,12 @@ impl U32FastFieldReader {
             let data_arr = &(data.deref()[8..]);
             BitUnpacker::new(data_arr, num_bits as usize)
         };
-        Ok(U32FastFieldReader {
+        U32FastFieldReader {
             _data: data,
             bit_unpacker: bit_unpacker,
             min_val: min_val,
             max_val: max_val,
-        })
+        }
     }
 
     pub fn get(&self, doc: DocId) -> u32 {
@@ -138,17 +142,20 @@ impl U32FastFieldsReader {
         })
     }
     
-    pub fn get_field(&self, field: Field) -> io::Result {
-        match self.field_offsets.get(&field) {
-            Some(&(start, stop)) => {
+    /// Returns the u32 fast value reader if the field
+    /// is a u32 field indexed as "fast".
+    ///
+    /// Return None if the field is not a u32 field
+    /// indexed with the fast option.
+    ///
+    /// # Panics
+    /// May panic if the index is corrupted.
+    pub fn get_field(&self, field: Field) -> Option {
+        self.field_offsets
+            .get(&field)
+            .map(|&(start, stop)| {
                 let field_source = self.source.slice(start as usize, stop as usize);
                 U32FastFieldReader::open(field_source)
-            }
-            None => {
-                Err(io::Error::new(io::ErrorKind::InvalidInput, "Could not find field"))
-            }
-
-        }
-
+            })
     }
 }
diff --git a/src/fastfield/writer.rs b/src/fastfield/writer.rs
index 4527533df..715182f36 100644
--- a/src/fastfield/writer.rs
+++ b/src/fastfield/writer.rs
@@ -98,7 +98,6 @@ impl U32FastFieldWriter {
                 }
             },
             None => {
-                // TODO make default value configurable
                 0u32
             }            
         }
diff --git a/src/functional_test.rs b/src/functional_test.rs
new file mode 100644
index 000000000..e8f8797dd
--- /dev/null
+++ b/src/functional_test.rs
@@ -0,0 +1,62 @@
+use std::collections::HashSet;
+use rand::thread_rng;
+
+use schema::*;
+use Index;
+use Searcher;
+use rand::distributions::{IndependentSample, Range};
+
+fn check_index_content(searcher: &Searcher, vals: &HashSet) {
+    assert!(searcher.segment_readers().len() < 20);
+    assert_eq!(searcher.num_docs() as usize, vals.len());
+}
+
+#[test]
+#[ignore]
+fn test_indexing() {
+
+    let mut schema_builder = SchemaBuilder::default();
+
+    let id_field = schema_builder.add_u32_field("id", U32_INDEXED);
+    let multiples_field = schema_builder.add_u32_field("multiples", U32_INDEXED);    
+    let schema = schema_builder.build();
+
+    let index = Index::create_from_tempdir(schema).unwrap();
+
+    let universe = Range::new(0u32, 20u32);
+    let mut rng = thread_rng();
+
+    let mut index_writer = index.writer_with_num_threads(3, 120_000_000).unwrap();
+
+    let mut committed_docs: HashSet = HashSet::new();
+    let mut uncommitted_docs: HashSet = HashSet::new();
+
+    for _ in 0..200 {
+        let random_val = universe.ind_sample(&mut rng);
+        if random_val == 0 {
+            index_writer.commit().expect("Commit failed");
+            committed_docs.extend(&uncommitted_docs);
+            uncommitted_docs.clear();
+            index.load_searchers().unwrap();
+            let searcher = index.searcher();
+            // check that everything is correct.
+            check_index_content(&searcher, &committed_docs);
+        }
+        else {
+            if committed_docs.remove(&random_val) ||
+               uncommitted_docs.remove(&random_val) {
+                let doc_id_term = Term::from_field_u32(id_field, random_val);
+                index_writer.delete_term(doc_id_term);
+            }
+            else {
+                uncommitted_docs.insert(random_val);
+                let mut doc = Document::new();
+                doc.add_u32(id_field, random_val);
+                for i in 1u32..10u32 {
+                    doc.add_u32(multiples_field, random_val * i);
+                }
+                index_writer.add_document(doc);
+            }
+        }
+    }
+}
diff --git a/src/indexer/delete_queue.rs b/src/indexer/delete_queue.rs
new file mode 100644
index 000000000..a031c63d3
--- /dev/null
+++ b/src/indexer/delete_queue.rs
@@ -0,0 +1,325 @@
+use super::operation::DeleteOperation;
+use std::sync::{Arc, RwLock};
+use std::mem;
+use std::ops::DerefMut;
+
+
+// The DeleteQueue is similar in conceptually to a multiple
+// consumer single producer broadcast channel.
+// 
+// All consumer will receive all messages.
+// 
+// Consumer of the delete queue are holding a `DeleteCursor`,
+// which points to a specific place of the `DeleteQueue`.
+// 
+// New consumer can be created in two ways
+// - calling `delete_queue.cursor()` returns a cursor, that 
+//   will include all future delete operation (and no past operations).
+// - cloning an existing cursor returns a new cursor, that
+//   is at the exact same position, and can now advance independantly 
+//   from the original cursor.
+#[derive(Default)]
+struct InnerDeleteQueue {
+    writer: Vec,
+    last_block: Option>,
+}
+
+#[derive(Clone, Default)]
+pub struct DeleteQueue {
+    inner: Arc>,
+}
+
+
+impl DeleteQueue {
+
+    // Creates a new delete queue.
+    pub fn new() -> DeleteQueue {
+        
+        let delete_queue = DeleteQueue {
+            inner: Arc::default(),
+        };
+            
+        let next_block = NextBlock::from(delete_queue.clone());
+        {
+            let mut delete_queue_wlock = delete_queue.inner.write().unwrap();
+            delete_queue_wlock.last_block = Some(
+                Arc::new(Block {
+                    operations: Arc::default(),
+                    next: next_block,
+                })
+            );
+        }
+
+        delete_queue
+    }
+    
+
+    // Creates a new cursor that makes it possible to 
+    // consume future delete operations.
+    // 
+    // Past delete operations are not accessible.
+    pub fn cursor(&self) -> DeleteCursor {
+        let last_block = self.inner
+            .read()
+            .expect("Read lock poisoned when opening delete queue cursor")
+            .last_block
+            .clone()
+            .expect("Failed to unwrap last_block. This should never happen
+                as the Option<> is only here to make
+                initialization possible");
+        let operations_len = last_block.operations.len();
+        DeleteCursor {
+            block: last_block,
+            pos: operations_len,
+        }
+    }
+
+    // Appends a new delete operations.
+    pub fn push(&self, delete_operation: DeleteOperation) {
+        self.inner
+            .write()
+            .expect("Failed to acquire write lock on delete queue writer")
+            .writer
+            .push(delete_operation);
+    }
+
+    // DeleteQueue is a linked list of blocks of
+    // delete operations.
+    // 
+    // Writing happens by simply appending to a vec.
+    // `.flush()` takes this pending delete operations vec
+    // creates a new read-only block from it, 
+    // and appends it to the linked list.
+    // 
+    // `.flush()` happens when, for instance, 
+    // a consumer reaches the last read-only operations.
+    // It then ask the delete queue if there happen to 
+    // be some unflushed operations.
+    //
+    fn flush(&self) -> Option> {
+        let mut self_wlock = self
+            .inner
+            .write()
+            .expect("Failed to acquire write lock on delete queue writer");
+        
+        let delete_operations;
+        {
+            let writer: &mut Vec = &mut self_wlock.writer;
+            if writer.is_empty() {
+                return None;
+            }
+            delete_operations = mem::replace(writer, vec!());
+        }
+
+        let next_block = NextBlock::from(self.clone());
+        {
+            self_wlock.last_block = Some(
+                Arc::new(Block {
+                    operations: Arc::new(delete_operations),
+                    next: next_block,
+                })
+            );
+        }
+        self_wlock.last_block.clone()
+    }
+}
+
+enum InnerNextBlock {
+    Writer(DeleteQueue),
+    Closed(Arc),
+}
+
+struct NextBlock(RwLock);
+
+impl From for NextBlock {
+    fn from(delete_queue: DeleteQueue) -> NextBlock {
+        NextBlock(RwLock::new(InnerNextBlock::Writer(delete_queue)))
+    }
+}
+
+impl NextBlock {   
+    fn next_block(&self) -> Option> {
+        {
+            let next_read_lock = self.0
+                .read()
+                .expect("Failed to acquire write lock in delete queue");
+            match *next_read_lock {
+                InnerNextBlock::Closed(ref block) => {
+                    return Some(block.clone());
+                }
+                _ => {}
+            }
+        }
+        let next_block;
+        {
+            let mut next_write_lock = self.0
+                .write()
+                .expect("Failed to acquire write lock in delete queue");
+            match *next_write_lock {
+                InnerNextBlock::Closed(ref block) => {
+                    return Some(block.clone());
+                }
+                InnerNextBlock::Writer(ref writer) => {
+                    match writer.flush() {
+                        Some(flushed_next_block) => {
+                            next_block = flushed_next_block;
+                        }
+                        None => {
+                            return None;
+                        }
+                    }
+                }
+            }
+            *next_write_lock.deref_mut() = InnerNextBlock::Closed(next_block.clone()); // TODO fix
+            return Some(next_block)
+        }
+    }
+}
+
+struct Block {
+    operations: Arc>,
+    next: NextBlock,
+}
+
+
+#[derive(Clone)]
+pub struct DeleteCursor {
+    block: Arc,
+    pos: usize,
+}
+
+
+impl DeleteCursor {  
+
+    /// Skips operations and position it so that
+    /// - either all of the delete operation currently in the 
+    ///   queue are consume and the next get will return None.
+    /// - the next get will return the first operation with an
+    /// `opstamp >= target_opstamp`.
+    pub fn skip_to(&mut self, target_opstamp: u64) {
+        // TODO Can be optimize as we work with block.
+        loop {
+            if let Some(operation) = self.get() {
+                if operation.opstamp >= target_opstamp {
+                    break;
+                }
+            }
+            else {
+                break;
+            }
+            self.advance();
+        }
+    }
+
+    /// If the current block has been entirely 
+    /// consumed, try to load the next one.
+    /// 
+    /// Return `true`, if after this attempt, 
+    /// the cursor is on a block that has not
+    /// been entirely consumed.
+    /// Return `false`, if we have reached the end of the queue.
+    fn load_block_if_required(&mut self) -> bool {
+        if self.pos >= self.block.operations.len() {
+            // we have consumed our operations entirely.
+            // let's ask our writer if he has more for us.
+            // self.go_next_block();
+            match self.block.next.next_block() {
+                Some(block) => {
+                    self.block = block;
+                    self.pos = 0;
+                    true
+                }
+                None => {
+                    false
+                }
+            }
+        }
+        else {
+            true
+        }
+    }
+    
+    /// Advance to the next delete operation.
+    /// Returns true iff there is such an operation.
+    pub fn advance(&mut self) -> bool {
+        if self.load_block_if_required() {
+            self.pos += 1;
+            true
+        }
+        else {
+            false
+        }
+    }
+
+    /// Get the current delete operation.
+    /// Calling `.get` does not advance the cursor.
+    pub fn get(&mut self) -> Option<&DeleteOperation> {
+        if self.load_block_if_required() {
+            Some(&self.block.operations[self.pos])
+        }
+        else {
+            None
+        }
+    }
+
+}
+
+
+
+
+
+
+#[cfg(test)]
+mod tests {
+
+    use super::{DeleteQueue, DeleteOperation};
+    use schema::{Term, Field};
+
+    #[test]
+    fn test_deletequeue() {
+        let delete_queue = DeleteQueue::new();
+        
+        let make_op = |i: usize| {
+            let field = Field(1u8);
+            DeleteOperation {
+                opstamp: i as u64,
+                term: Term::from_field_u32(field, i as u32)
+            }
+        };
+
+        delete_queue.push(make_op(1));
+        delete_queue.push(make_op(2));
+
+        let snapshot = delete_queue.cursor();
+        {
+            let mut operations_it = snapshot.clone();
+            assert_eq!(operations_it.get().unwrap().opstamp, 1);
+            operations_it.advance();
+            assert_eq!(operations_it.get().unwrap().opstamp, 2);
+            operations_it.advance();
+            assert!(operations_it.get().is_none());
+            operations_it.advance();
+        
+            let mut snapshot2 = delete_queue.cursor();
+            assert!(snapshot2.get().is_none());
+            delete_queue.push(make_op(3));
+            assert_eq!(snapshot2.get().unwrap().opstamp, 3);
+            assert_eq!(operations_it.get().unwrap().opstamp, 3);
+            assert_eq!(operations_it.get().unwrap().opstamp, 3);
+            operations_it.advance();
+            assert!(operations_it.get().is_none());
+            operations_it.advance();
+        }
+        {   
+            let mut operations_it = snapshot.clone();
+            assert_eq!(operations_it.get().unwrap().opstamp, 1);
+            operations_it.advance();
+            assert_eq!(operations_it.get().unwrap().opstamp, 2);
+            operations_it.advance();
+            assert_eq!(operations_it.get().unwrap().opstamp, 3);
+            operations_it.advance();
+            assert!(operations_it.get().is_none());
+        }
+        
+    }
+}
\ No newline at end of file
diff --git a/src/indexer/directory_lock.rs b/src/indexer/directory_lock.rs
index 0b29e127a..db149a297 100644
--- a/src/indexer/directory_lock.rs
+++ b/src/indexer/directory_lock.rs
@@ -1,8 +1,7 @@
 use Directory;
-use std::path::Path;
 use directory::error::OpenWriteError;
+use core::LOCKFILE_FILEPATH;
 
-pub const LOCKFILE_NAME: &'static str = ".tantivy-indexer.lock";
 
 
 /// The directory lock is a mechanism used to
@@ -16,16 +15,14 @@ pub struct DirectoryLock {
 
 impl DirectoryLock {
     pub fn lock(mut directory: Box) -> Result {
-        let lockfile_path = Path::new(LOCKFILE_NAME);
-        try!(directory.open_write(lockfile_path));
+        try!(directory.open_write(&*LOCKFILE_FILEPATH));
         Ok(DirectoryLock { directory: directory })
     }
 }
 
 impl Drop for DirectoryLock {
     fn drop(&mut self) {
-        let lockfile_path = Path::new(LOCKFILE_NAME);
-        if let Err(e) = self.directory.delete(lockfile_path) {
+        if let Err(e) = self.directory.delete(&*LOCKFILE_FILEPATH) {
             error!("Failed to remove the lock file. {:?}", e);
         }
     }
diff --git a/src/indexer/doc_opstamp_mapping.rs b/src/indexer/doc_opstamp_mapping.rs
new file mode 100644
index 000000000..16eb1ff28
--- /dev/null
+++ b/src/indexer/doc_opstamp_mapping.rs
@@ -0,0 +1,93 @@
+use std::sync::Arc;
+use DocId;
+
+
+// Doc to opstamp is used to identify which
+// document should be deleted.
+// 
+// Since the docset matching the query of a delete operation
+// is not computed right when the delete operation is received,
+// we need to find a way to evaluate, for each document,
+// whether the document was added before or after
+// the delete operation. This anteriority is used by comparing
+// the docstamp of the document.
+//
+// The doc to opstamp mapping stores precisely an array
+// indexed by doc id and storing the opstamp of the document.
+// 
+// This mapping is (for the moment) stricly increasing
+// because of the way document id are allocated.
+#[derive(Clone)]
+pub enum DocToOpstampMapping {
+    WithMap(Arc>),
+    None
+}
+
+impl From> for DocToOpstampMapping {
+    fn from(opstamps: Vec) -> DocToOpstampMapping {
+        DocToOpstampMapping::WithMap(Arc::new(opstamps))
+    }
+}
+
+impl DocToOpstampMapping {
+    
+    /// Given an opstamp return the limit doc id L
+    /// such that all doc id D such that 
+    // D >= L iff opstamp(D) >= than `target_opstamp`.
+    //
+    // The edge case opstamp = some doc opstamp is in practise
+    // never called.
+    pub fn compute_doc_limit(&self, target_opstamp: u64) -> DocId {
+        match *self {
+            DocToOpstampMapping::WithMap(ref doc_opstamps) => {
+                match doc_opstamps.binary_search(&target_opstamp) {
+                    Ok(doc_id) => doc_id as DocId,
+                    Err(doc_id) => doc_id as DocId,
+                }
+            }
+            DocToOpstampMapping::None => DocId::max_value(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::DocToOpstampMapping;
+
+    #[test]
+    fn test_doc_to_opstamp_mapping_none() {
+        let doc_to_opstamp_mapping = DocToOpstampMapping::None;
+        assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(1), u32::max_value());
+    }
+
+    #[test]
+    fn test_doc_to_opstamp_mapping_complex() {
+        {
+            let doc_to_opstamp_mapping = DocToOpstampMapping::from(vec!());
+            assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(0u64), 0);
+            assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(2u64), 0);
+        }
+        {
+            let doc_to_opstamp_mapping = DocToOpstampMapping::from(vec!(1u64));
+            assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(0u64), 0);
+            assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(2u64), 1);
+        }
+        {
+            let doc_to_opstamp_mapping = DocToOpstampMapping::from(vec!(1u64, 12u64, 17u64, 23u64));
+            assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(0u64), 0);
+            for i in 2u64..13u64 {
+                assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(i), 1);
+            }
+            for i in 13u64..18u64 {
+                assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(i), 2);
+            }
+            for i in 18u64..24u64 {
+                assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(i), 3);
+            }
+            for i in 24u64..30u64 {
+                assert_eq!(doc_to_opstamp_mapping.compute_doc_limit(i), 4);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/indexer/index_writer.rs b/src/indexer/index_writer.rs
index a7aaaf9b0..48d76a576 100644
--- a/src/indexer/index_writer.rs
+++ b/src/indexer/index_writer.rs
@@ -1,30 +1,38 @@
-use schema::Schema;
-use schema::Document;
-use indexer::SegmentSerializer;
-use core::SerializableSegment;
+use bit_set::BitSet;
+use chan;
 use core::Index;
 use core::Segment;
-use std::thread::JoinHandle;
-use indexer::{MergePolicy, DefaultMergePolicy};
-use indexer::SegmentWriter;
-use super::directory_lock::DirectoryLock;
-use std::clone::Clone;
-use std::io;
-use std::thread;
-use std::mem;
-use indexer::merger::IndexMerger;
+use core::SegmentComponent;
 use core::SegmentId;
-use datastruct::stacker::Heap;
-use std::mem::swap;
-use std::sync::{Arc, Mutex};
-use chan;
 use core::SegmentMeta;
-use super::segment_updater::{SegmentUpdater, SegmentUpdate, SegmentUpdateSender};
-use std::time::Duration;
-use super::super::core::index::get_segment_manager;
-use super::segment_manager::CommitState;
-use Result;
+use core::SegmentReader;
+use indexer::stamper::Stamper;
+use datastruct::stacker::Heap;
+use directory::FileProtection;
 use Error;
+use Directory;
+use fastfield::delete::write_delete_bitset;
+use indexer::delete_queue::{DeleteCursor, DeleteQueue};
+use futures::Canceled;
+use futures::Future;
+use indexer::doc_opstamp_mapping::DocToOpstampMapping;
+use indexer::MergePolicy;
+use indexer::operation::DeleteOperation;
+use indexer::SegmentEntry;
+use indexer::SegmentWriter;
+use postings::DocSet;
+use postings::SegmentPostingsOption;
+use Result;
+use schema::Document;
+use schema::Schema;
+use schema::Term;
+use std::mem;
+use std::mem::swap; 
+use std::thread::JoinHandle;
+use super::directory_lock::DirectoryLock;
+use super::operation::AddOperation;
+use super::segment_updater::SegmentUpdater;
+use std::thread;
 
 // Size of the margin for the heap. A segment is closed when the remaining memory
 // in the heap goes below MARGIN_IN_BYTES.
@@ -36,12 +44,8 @@ pub const HEAP_SIZE_LIMIT: u32 = MARGIN_IN_BYTES * 3u32;
 // Add document will block if the number of docs waiting in the queue to be indexed reaches PIPELINE_MAX_SIZE_IN_DOCS
 const PIPELINE_MAX_SIZE_IN_DOCS: usize = 10_000;
 
-
-
-type DocumentSender = chan::Sender;
-type DocumentReceiver = chan::Receiver;
-
-
+type DocumentSender = chan::Sender;
+type DocumentReceiver = chan::Receiver;
 
 /// `IndexWriter` is the user entry-point to add document to an index.
 ///
@@ -55,9 +59,8 @@ pub struct IndexWriter {
     // lifetime of the lock with that of the IndexWriter.
     _directory_lock: DirectoryLock, 
     
-    _merge_policy: Arc>>,
-    
     index: Index,
+
     heap_size_in_bytes_per_thread: usize,
 
     workers_join_handle: Vec>>,
@@ -65,15 +68,18 @@ pub struct IndexWriter {
     document_receiver: DocumentReceiver,
     document_sender: DocumentSender,
 
-    segment_update_sender: SegmentUpdateSender,
-    segment_update_thread: JoinHandle<()>,
+    segment_updater: SegmentUpdater,
 
     worker_id: usize,
 
     num_threads: usize,
 
-    uncommitted_docstamp: u64,
-    committed_docstamp: u64,
+    generation: usize,
+
+    delete_queue: DeleteQueue,
+
+    stamper: Stamper,
+    committed_opstamp: u64,
 }
 
 // IndexWriter cannot be sent to another thread.
@@ -81,15 +87,185 @@ impl !Send for IndexWriter {}
 impl !Sync for IndexWriter {}
 
 
+
+/// Open a new index writer. Attempts to acquire a lockfile.
+///
+/// The lockfile should be deleted on drop, but it is possible
+/// that due to a panic or other error, a stale lockfile will be
+/// left in the index directory. If you are sure that no other
+/// `IndexWriter` on the system is accessing the index directory,
+/// it is safe to manually delete the lockfile.
+///
+/// num_threads specifies the number of indexing workers that
+/// should work at the same time.
+/// # Errors
+/// If the lockfile already exists, returns `Error::FileAlreadyExists`.
+/// # Panics
+/// If the heap size per thread is too small, panics.
+pub fn open_index_writer(
+    index: &Index,
+    num_threads: usize,
+    heap_size_in_bytes_per_thread: usize) -> Result {
+
+    if heap_size_in_bytes_per_thread <= HEAP_SIZE_LIMIT as usize {
+        panic!(format!("The heap size per thread needs to be at least {}.",
+                        HEAP_SIZE_LIMIT));
+    }
+    
+    let directory_lock = try!(DirectoryLock::lock(index.directory().box_clone()));
+    
+    let (document_sender, document_receiver): (DocumentSender, DocumentReceiver) =
+        chan::sync(PIPELINE_MAX_SIZE_IN_DOCS);
+
+
+    let delete_queue = DeleteQueue::new();
+    
+    let stamper = Stamper::new(index.opstamp());
+
+    let segment_updater = SegmentUpdater::new(index.clone(), 
+                                              stamper.clone(),
+                                              delete_queue.cursor())?;
+    
+    let mut index_writer = IndexWriter {
+        
+        _directory_lock: directory_lock,
+        
+        heap_size_in_bytes_per_thread: heap_size_in_bytes_per_thread,
+        index: index.clone(),
+
+        document_receiver: document_receiver,
+        document_sender: document_sender,
+
+        segment_updater: segment_updater,
+
+        workers_join_handle: vec!(),
+        num_threads: num_threads,
+
+        delete_queue: delete_queue,
+
+        committed_opstamp: index.opstamp(),
+        stamper: stamper,
+
+        generation: 0,
+
+        worker_id: 0,
+    };
+    try!(index_writer.start_workers());
+    Ok(index_writer)
+}
+
+
+
+pub fn compute_deleted_bitset(
+    delete_bitset: &mut BitSet,
+    segment_reader: &SegmentReader,
+    delete_cursor: &mut DeleteCursor,
+    doc_opstamps: DocToOpstampMapping,
+    target_opstamp: u64) -> Result {
+    
+    let mut might_have_changed = false;
+    
+    loop {
+        if let Some(delete_op) = delete_cursor.get() {
+            if delete_op.opstamp > target_opstamp {
+                break;
+            }
+            else {
+                // A delete operation should only affect
+                // document that were inserted after it.
+                // 
+                // Limit doc helps identify the first document
+                // that may be affected by the delete operation.
+                let limit_doc = doc_opstamps.compute_doc_limit(delete_op.opstamp);
+                if let Some(mut docset) = segment_reader.read_postings(&delete_op.term, SegmentPostingsOption::NoFreq) {
+                    while docset.advance() {
+                        let deleted_doc = docset.doc();
+                        if deleted_doc < limit_doc {
+                            delete_bitset.insert(deleted_doc as usize);
+                            might_have_changed = true;
+                        }
+                    }
+                }
+            }
+        }
+        else {
+            break;
+        }
+        delete_cursor.advance();
+    }
+    Ok(might_have_changed)
+}
+
+
+// TODO skip delete operation before teh 
+// last delete opstamp
+
+/// Advance delete for the given segment up
+/// to the target opstamp.
+pub fn advance_deletes(
+    mut segment: Segment,
+    segment_entry: &mut SegmentEntry,
+    target_opstamp: u64) -> Result> {
+
+    let mut file_protect: Option = None;
+
+    {
+        if let Some(previous_opstamp) = segment_entry.meta().delete_opstamp() {
+            // We are already up-to-date here.
+            if target_opstamp == previous_opstamp {
+                return Ok(file_protect);
+            }
+        }
+        let segment_reader = SegmentReader::open(segment.clone())?;
+        let max_doc = segment_reader.max_doc();
+        
+        let mut delete_bitset: BitSet =
+            match segment_entry.delete_bitset() {
+                Some(ref previous_delete_bitset) =>
+                    (*previous_delete_bitset).clone(),
+                None =>
+                    BitSet::with_capacity(max_doc as usize)
+            };
+        
+        let delete_cursor = segment_entry.delete_cursor();
+
+        compute_deleted_bitset(
+            &mut delete_bitset,
+            &segment_reader,
+            delete_cursor,
+            DocToOpstampMapping::None,
+            target_opstamp)?;
+        
+        for doc in 0u32..max_doc {
+            if segment_reader.is_deleted(doc) {
+                delete_bitset.insert(doc as usize);
+            }
+        }
+
+        let num_deleted_docs = delete_bitset.len();
+        if num_deleted_docs > 0 {
+            segment.set_delete_meta(num_deleted_docs as u32, target_opstamp);
+            file_protect = Some(segment.protect_from_delete(SegmentComponent::DELETE));
+            let mut delete_file = segment.open_write(SegmentComponent::DELETE)?;
+            write_delete_bitset(&delete_bitset, &mut delete_file)?;
+        }
+    }
+    segment_entry.set_meta(segment.meta().clone());
+
+    Ok(file_protect)
+}
+
 fn index_documents(heap: &mut Heap,
                    segment: Segment,
                    schema: &Schema,
-                   document_iterator: &mut Iterator,
-                   segment_update_sender: &mut SegmentUpdateSender)
-                   -> Result<()> {
+                   generation: usize,
+                   document_iterator: &mut Iterator,
+                   segment_updater: &mut SegmentUpdater,
+                   mut delete_cursor: DeleteCursor)
+                   -> Result {
     heap.clear();
     let segment_id = segment.id();
-    let mut segment_writer = try!(SegmentWriter::for_segment(heap, segment, &schema));
+    let mut segment_writer = SegmentWriter::for_segment(heap, segment.clone(), &schema)?;
     for doc in document_iterator {
         try!(segment_writer.add_document(&doc, &schema));
         if segment_writer.is_buffer_full() {
@@ -99,31 +275,55 @@ fn index_documents(heap: &mut Heap,
         }
     }
     let num_docs = segment_writer.max_doc();
-    let segment_meta = SegmentMeta {
-        segment_id: segment_id,
-        num_docs: num_docs,
-    };
+    
+    // this is ensured by the call to peek before starting
+    // the worker thread.
+    assert!(num_docs > 0);    
 
-    try!(segment_writer.finalize());
-    segment_update_sender.send(SegmentUpdate::AddSegment(segment_meta));
-    Ok(())
+    let doc_opstamps: Vec = segment_writer.finalize()?;
 
-}
+    let mut segment_meta = SegmentMeta::new(segment_id);
+    segment_meta.set_max_doc(num_docs);
+
+    let last_docstamp: u64 = *(doc_opstamps.last().unwrap());
+    
+    let doc_to_opstamps = DocToOpstampMapping::from(doc_opstamps);
+    let segment_reader = SegmentReader::open(segment)?;
+    let mut deleted_bitset = BitSet::with_capacity(num_docs as usize);
+    let may_have_deletes = compute_deleted_bitset(
+        &mut deleted_bitset,
+        &segment_reader,
+        &mut delete_cursor,
+        doc_to_opstamps,
+        last_docstamp,
+    )?;
+
+    let segment_entry = SegmentEntry::new(
+        segment_meta,
+        delete_cursor,
+        { if may_have_deletes { Some(deleted_bitset) }
+          else { None } }
+    );
+    
+    Ok(
+        segment_updater
+        .add_segment(generation, segment_entry)
+    )
+        
+}   
 
 
 impl IndexWriter {
     /// The index writer
     pub fn wait_merging_threads(mut self) -> Result<()> {
-
-        self.segment_update_sender.send(SegmentUpdate::Terminate);
         
         // this will stop the indexing thread,
-        // dropping the last reference to the segment_update_sender.
+        // dropping the last reference to the segment_updater.
         drop(self.document_sender);
         
-        let mut v = Vec::new();
-        mem::swap(&mut v, &mut self.workers_join_handle);
-        for join_handle in v {
+        
+        let former_workers_handles = mem::replace(&mut self.workers_join_handle, vec!());
+        for join_handle in former_workers_handles {
             try!(join_handle.join()
                 .expect("Indexing Worker thread panicked")
                 .map_err(|e| {
@@ -131,122 +331,84 @@ impl IndexWriter {
                 }));
         }
         drop(self.workers_join_handle);
-        self.segment_update_thread
-            .join()
-            .map_err(|err| {
-                error!("Error in the merging thread {:?}", err);
-                Error::ErrorInThread(format!("{:?}", err))
-            })
+
+        let result = self.segment_updater
+            .wait_merging_thread()
+            .map_err(|_| 
+                Error::ErrorInThread("Failed to join merging thread.".to_string())
+            );
+        
+        if let &Err(ref e) = &result {
+            error!("Some merging thread failed {:?}", e);
+        }
+
+        result
     }
 
     /// Spawns a new worker thread for indexing.
     /// The thread consumes documents from the pipeline.
     ///
     fn add_indexing_worker(&mut self) -> Result<()> {
-        let index = self.index.clone();
         let schema = self.index.schema();
         let document_receiver_clone = self.document_receiver.clone();
-        let mut segment_update_sender = self.segment_update_sender.clone();
+        let mut segment_updater = self.segment_updater.clone();
         let mut heap = Heap::with_capacity(self.heap_size_in_bytes_per_thread);
-        let join_handle: JoinHandle> = try!(thread::Builder::new()
-            .name(format!("indexing_thread_{}", self.worker_id))
+        
+        let generation = self.generation;
+        
+        let mut delete_cursor = self.delete_queue.cursor();
+
+        let join_handle: JoinHandle> =
+            thread::Builder::new()
+            .name(format!("indexing thread {} for gen {}", self.worker_id, generation))
             .spawn(move || {
+                
                 loop {
-                    let segment = index.new_segment();
+
                     let mut document_iterator = document_receiver_clone.clone()
                         .into_iter()
                         .peekable();
+                    
                     // the peeking here is to avoid
                     // creating a new segment's files
                     // if no document are available.
-                    if document_iterator.peek().is_some() {
-                        try!(index_documents(&mut heap,
-                                             segment,
-                                             &schema,
-                                             &mut document_iterator,
-                                             &mut segment_update_sender));
-                    } else {
+                    //
+                    // this is a valid guarantee as the 
+                    // peeked document now belongs to
+                    // our local iterator.
+                    if let Some(operation) = document_iterator.peek() {
+                        delete_cursor.skip_to(operation.opstamp);
+                    }
+                    else {
                         // No more documents.
                         // Happens when there is a commit, or if the `IndexWriter`
                         // was dropped.
-                        return Ok(());
+                        return Ok(())
                     }
+                    let segment = segment_updater.new_segment();
+                    index_documents(&mut heap,
+                                    segment,
+                                    &schema,
+                                    generation,
+                                    &mut document_iterator,
+                                    &mut segment_updater,
+                                    delete_cursor.clone())?;
+                    
                 }
-            }));
+            })?;
         self.worker_id += 1;
         self.workers_join_handle.push(join_handle);
         Ok(())
     }
 
-
-    /// Open a new index writer. Attempts to acquire a lockfile.
-    ///
-    /// The lockfile should be deleted on drop, but it is possible
-    /// that due to a panic or other error, a stale lockfile will be
-    /// left in the index directory. If you are sure that no other
-    /// `IndexWriter` on the system is accessing the index directory,
-    /// it is safe to manually delete the lockfile.
-    ///
-    /// num_threads specifies the number of indexing workers that
-    /// should work at the same time.
-    /// # Errors
-    /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
-    /// # Panics
-    /// If the heap size per thread is too small, panics.
-    pub fn open(index: &Index,
-                num_threads: usize,
-                heap_size_in_bytes_per_thread: usize)
-                -> Result {
-
-        if heap_size_in_bytes_per_thread <= HEAP_SIZE_LIMIT as usize {
-            panic!(format!("The heap size per thread needs to be at least {}.",
-                           HEAP_SIZE_LIMIT));
-        }
-        
-        let directory_lock = try!(DirectoryLock::lock(index.directory().box_clone()));
-        
-        let (document_sender, document_receiver): (DocumentSender, DocumentReceiver) =
-            chan::sync(PIPELINE_MAX_SIZE_IN_DOCS);
-        
-        let merge_policy: Arc>> = Arc::new(Mutex::new(box DefaultMergePolicy::default()));
-        
-        let (segment_update_sender, segment_update_thread) = SegmentUpdater::start_updater(index.clone(), merge_policy.clone());
-        
-        let mut index_writer = IndexWriter {
-            
-            _directory_lock: directory_lock,
-            
-            _merge_policy: merge_policy,
-            
-            heap_size_in_bytes_per_thread: heap_size_in_bytes_per_thread,
-            index: index.clone(),
-
-            document_receiver: document_receiver,
-            document_sender: document_sender,
-
-            segment_update_sender: segment_update_sender,
-            segment_update_thread: segment_update_thread,
-
-            workers_join_handle: Vec::new(),
-            num_threads: num_threads,
-
-            committed_docstamp: index.docstamp(),
-            uncommitted_docstamp: index.docstamp(),
-            worker_id: 0,
-        };
-        try!(index_writer.start_workers());
-        Ok(index_writer)
-    }
-    
-    
-    /// Returns a clone of the index_writer merge policy.
+    /// Accessor to the merge policy.
     pub fn get_merge_policy(&self) -> Box {
-        self._merge_policy.lock().unwrap().box_clone() 
+        self.segment_updater.get_merge_policy()
     }
-    
+
     /// Set the merge policy.
     pub fn set_merge_policy(&self, merge_policy: Box) {
-        *self._merge_policy.lock().unwrap() = merge_policy;
+        self.segment_updater.set_merge_policy(merge_policy);
     }
     
     fn start_workers(&mut self) -> Result<()> {
@@ -257,55 +419,8 @@ impl IndexWriter {
     }
 
     /// Merges a given list of segments
-    pub fn merge(&mut self, segments: &[Segment]) -> Result<()> {
-
-        if segments.len() < 2 {
-            // no segments or one segment? nothing to do.
-            return Ok(());
-        }
-
-
-        let segment_manager = get_segment_manager(&self.index);
-
-        {
-            // let's check that all these segments are in the same
-            // committed/uncommited state.
-            let first_commit_state = segment_manager.is_committed(segments[0].id());
-
-            for segment in segments {
-                let commit_state = segment_manager.is_committed(segment.id());
-                if commit_state == CommitState::Missing {
-                    return Err(Error::InvalidArgument(format!("Segment {:?} is not in the index",
-                                                              segments[0].id())));
-                }
-                if commit_state != first_commit_state {
-                    return Err(Error::InvalidArgument(String::from("You may not merge segments \
-                                                                    that are heterogenously in \
-                                                                    committed and uncommited.")));
-                }
-            }
-        }
-
-        let schema = self.index.schema();
-
-        // An IndexMerger is like a "view" of our merged segments.
-        let merger = try!(IndexMerger::open(schema, segments));
-        let mut merged_segment = self.index.new_segment();
-
-        // ... we just serialize this index merger in our new segment
-        // to merge the two segments.
-        let segment_serializer = try!(SegmentSerializer::for_segment(&mut merged_segment));
-        let num_docs = try!(merger.write(segment_serializer));
-        let merged_segment_ids: Vec =
-            segments.iter().map(|segment| segment.id()).collect();
-        let segment_meta = SegmentMeta {
-            segment_id: merged_segment.id(),
-            num_docs: num_docs,
-        };
-
-        segment_manager.end_merge(&merged_segment_ids, &segment_meta);
-        try!(self.index.load_searchers());
-        Ok(())
+    pub fn merge(&mut self, segment_ids: &[SegmentId]) -> impl Future {
+        self.segment_updater.start_merge(segment_ids)
     }
 
     /// Closes the current document channel send.
@@ -331,55 +446,28 @@ impl IndexWriter {
     /// After calling rollback, the index is in the same
     /// state as it was after the last commit.
     ///
-    /// The docstamp at the last commit is returned.
-    pub fn rollback(&mut self) -> Result {
+    /// The opstamp at the last commit is returned.
+    pub fn rollback(mut self) -> Result {
+        info!("Rolling back to opstamp {}", self.committed_opstamp);
 
-        self.segment_update_sender.send(SegmentUpdate::CancelGeneration);
-
-        // we cannot drop segment ready receiver yet
-        // as it would block the workers.
-        let document_receiver = self.recreate_document_channel();
+        self.segment_updater.kill();
 
         // Drains the document receiver pipeline :
         // Workers don't need to index the pending documents.
-        for _ in document_receiver {}
-
-        let mut former_workers_join_handle = Vec::new();
-        swap(&mut former_workers_join_handle,
-             &mut self.workers_join_handle);
-
-        // wait for all the worker to finish their work
-        // (it should be fast since we consumed all pending documents)
-        for worker_handle in former_workers_join_handle {
-            // we stop one worker at a time ...
-            try!(try!(worker_handle.join()
-                .map_err(|e| Error::ErrorInThread(format!("{:?}", e)))));
-            // ... and recreate a new one right away
-            // to work on the next generation.
-            try!(self.add_indexing_worker());
-        }
-
-        // All of our indexing workers for the rollbacked generation have
-        // been terminated.
-        // Our document receiver pipe was drained.
-        // No new document have been added in the meanwhile because `IndexWriter`
-        // is not shared by different threads.
-        //
-        // We can now open a new generation and reaccept segments
-        // from now on.
-        self.segment_update_sender.send(SegmentUpdate::NewGeneration);
-
-        let rollbacked_segments = get_segment_manager(&self.index).rollback();
-        for segment_id in rollbacked_segments {
-
-            // TODO all delete must happen after saving
-            // meta.json
-            self.index.delete_segment(segment_id);
-        }
+        let receiver_clone = self.document_receiver.clone();
+        let index = self.index.clone();
+        let num_threads = self.num_threads;
+        let heap_size_in_bytes_per_thread = self.heap_size_in_bytes_per_thread;
+        drop(self);
+        for _ in receiver_clone {}
         
-        // reset the docstamp
-        self.uncommitted_docstamp = self.committed_docstamp;
-        Ok(self.committed_docstamp)
+        let index_writer = open_index_writer(
+                &index,
+                num_threads,
+                heap_size_in_bytes_per_thread)?;
+        
+        Ok(index_writer)
+
     }
 
 
@@ -394,29 +482,11 @@ impl IndexWriter {
     /// long as the hard disk is spared), it will be possible
     /// to resume indexing from this point.
     ///
-    /// Commit returns the `docstamp` of the last document
+    /// Commit returns the `opstamp` of the last document
     /// that made it in the commit.
     ///
     pub fn commit(&mut self) -> Result {
 
-        // this will drop the current document channel
-        // and recreate a new one channels.
-        self.recreate_document_channel();
-
-        // Docstamp of the last document in this commit.
-        self.committed_docstamp = self.uncommitted_docstamp;
-
-        let mut former_workers_join_handle = Vec::new();
-        swap(&mut former_workers_join_handle,
-             &mut self.workers_join_handle);
-
-        for worker_handle in former_workers_join_handle {
-            let indexing_worker_result = try!(worker_handle.join()
-                .map_err(|e| Error::ErrorInThread(format!("{:?}", e))));
-            try!(indexing_worker_result);
-            // add a new worker for the next generation.
-            try!(self.add_indexing_worker());
-        }
         // here, because we join all of the worker threads,
         // all of the segment update for this commit have been
         // sent.
@@ -427,44 +497,96 @@ impl IndexWriter {
 
         // This will move uncommitted segments to the state of
         // committed segments.
-        self.segment_update_sender.send(SegmentUpdate::Commit(self.committed_docstamp));
+        self.committed_opstamp = self.stamper.stamp();
+        info!("committing {}", self.committed_opstamp);
 
-        // wait for the segment update thread to have processed the info
-        let segment_manager = get_segment_manager(&self.index);
-        while segment_manager.docstamp() != self.committed_docstamp {
-            thread::sleep(Duration::from_millis(100));
+        // this will drop the current document channel
+        // and recreate a new one channels.
+        self.recreate_document_channel();
+
+        let mut former_workers_join_handle = Vec::new();
+        swap(&mut former_workers_join_handle,
+             &mut self.workers_join_handle);
+        
+        for worker_handle in former_workers_join_handle {
+            let indexing_worker_result = try!(worker_handle.join()
+                .map_err(|e| Error::ErrorInThread(format!("{:?}", e))));
+            try!(indexing_worker_result);
+            // add a new worker for the next generation.
+            try!(self.add_indexing_worker());
         }
 
-        Ok(self.committed_docstamp)
+        
+
+        // wait for the segment update thread to have processed the info
+        self.segment_updater
+            .commit(self.committed_opstamp)?;
+        
+        Ok(self.committed_opstamp)
+    }    
+
+    /// Delete all documents containing a given term.
+    ///
+    /// Delete operation only affects documents that
+    /// were added in previous commits, and documents
+    /// that were added previously in the same commit.
+    ///
+    /// Like adds, the deletion itself will be visible 
+    /// only after calling `commit()`.
+    pub fn delete_term(&mut self, term: Term) -> u64 {
+        let opstamp = self.stamper.stamp();
+        let delete_operation = DeleteOperation {
+            opstamp: opstamp,
+            term: term,
+        };
+        self.delete_queue.push(delete_operation);
+        opstamp
     }
 
+    /// Returns the opstamp of the last successful commit.
+    /// 
+    /// This is, for instance, the opstamp the index will
+    /// rollback to if there is a failure like a power surge.
+    ///
+    /// This is also the opstamp of the commit that is currently
+    /// available for searchers.
+    pub fn commit_opstamp(&self) -> u64 {
+        self.committed_opstamp
+    }
 
     /// Adds a document.
     ///
     /// If the indexing pipeline is full, this call may block.
     ///
-    /// The docstamp is an increasing `u64` that can
+    /// The opstamp is an increasing `u64` that can
     /// be used by the client to align commits with its own
     /// document queue.
     ///
     /// Currently it represents the number of documents that
     /// have been added since the creation of the index.
-    pub fn add_document(&mut self, doc: Document) -> io::Result {
-        self.document_sender.send(doc);
-        self.uncommitted_docstamp += 1;
-        Ok(self.uncommitted_docstamp)
+    pub fn add_document(&mut self, document: Document) -> u64 {
+        let opstamp = self.stamper.stamp();
+        let add_operation = AddOperation {
+            opstamp: opstamp,
+            document: document,
+        };
+        self.document_sender.send(add_operation);
+        opstamp
     }
 }
 
+
+
+
 #[cfg(test)]
 mod tests {
 
-
+    use indexer::NoMergePolicy;
     use schema::{self, Document};
     use Index;
     use Term;
     use Error;
-    use indexer::NoMergePolicy;
+    use env_logger;
 
     #[test]
     fn test_lockfile_stops_duplicates() {
@@ -506,7 +628,6 @@ mod tests {
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
 
-
         let num_docs_containing = |s: &str| {
             let searcher = index.searcher();
             let term_a = Term::from_field_text(text_field, s);
@@ -519,32 +640,38 @@ mod tests {
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
-            assert_eq!(index_writer.rollback().unwrap(), 0u64);
+
+            index_writer = index_writer.rollback().unwrap();
+            
+            assert_eq!(index_writer.commit_opstamp(), 0u64);
             assert_eq!(num_docs_containing("a"), 0);
 
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "b");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             assert_eq!(index_writer.commit().unwrap(), 2u64);
-
+            index.load_searchers().unwrap();
             assert_eq!(num_docs_containing("a"), 0);
             assert_eq!(num_docs_containing("b"), 1);
             assert_eq!(num_docs_containing("c"), 1);
         }
+        index.load_searchers().unwrap();
         index.searcher();
     }
 
+
     #[test]
     fn test_with_merges() {
+        let _ = env_logger::init();
         let mut schema_builder = schema::SchemaBuilder::default();
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
@@ -556,23 +683,26 @@ mod tests {
         {
             // writing the segment
             let mut index_writer = index.writer_with_num_threads(4, 4 * 30_000_000).unwrap();
-            // create 10 segments with 100 tiny docs
+            // create 8 segments with 100 tiny docs
             for _doc in 0..100 {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().expect("commit failed");
             for _doc in 0..100 {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             // this should create 8 segments and trigger a merge.
             index_writer.commit().expect("commit failed");
             index_writer.wait_merging_threads().expect("waiting merging thread failed");
+            index.load_searchers().unwrap();
+            
             assert_eq!(num_docs_containing("a"), 200);
-            assert_eq!(index.searchable_segments().len(), 1);
+            assert!(index.searchable_segments().unwrap().len() < 8);
+            
         }
     }
 
diff --git a/src/indexer/log_merge_policy.rs b/src/indexer/log_merge_policy.rs
index 5ca049e4c..951af8c31 100644
--- a/src/indexer/log_merge_policy.rs
+++ b/src/indexer/log_merge_policy.rs
@@ -48,13 +48,12 @@ impl LogMergePolicy {
 
 impl MergePolicy for LogMergePolicy {
     fn compute_merge_candidates(&self, segments: &[SegmentMeta]) -> Vec {
-
         if segments.is_empty() {
             return Vec::new();
         }
 
         let mut size_sorted_tuples = segments.iter()
-            .map(|x| x.num_docs)
+            .map(|x| x.num_docs())
             .enumerate()
             .collect::>();
 
@@ -75,16 +74,15 @@ impl MergePolicy for LogMergePolicy {
             levels.last_mut().unwrap().push(ind);
         }
 
-        let result = levels.iter()
+        levels
+            .iter()
             .filter(|level| level.len() >= self.min_merge_size)
             .map(|ind_vec| {
                 MergeCandidate(ind_vec.iter()
-                    .map(|&ind| segments[ind].segment_id)
+                    .map(|&ind| segments[ind].id())
                     .collect())
             })
-            .collect();
-
-        result
+            .collect()
     }
     
     fn box_clone(&self) -> Box {
@@ -122,11 +120,17 @@ mod tests {
         assert!(result_list.is_empty());
     }
 
+    fn seg_meta(num_docs: u32) -> SegmentMeta {
+        let mut segment_metas = SegmentMeta::new(SegmentId::generate_random());
+        segment_metas.set_max_doc(num_docs);
+        segment_metas
+    }
+
     #[test]
     fn test_log_merge_policy_pair() {
-        let test_input = vec![SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 10)];
+        let test_input = vec![seg_meta(10),
+                              seg_meta(10),
+                              seg_meta(10)];
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 1);
     }
@@ -134,12 +138,12 @@ mod tests {
     #[test]
     fn test_log_merge_policy_levels() {
         // multiple levels all get merged correctly
-        let test_input = vec![SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000)];
+        let test_input = vec![seg_meta(10),
+                              seg_meta(10),
+                              seg_meta(10),
+                              seg_meta(1000),
+                              seg_meta(1000),
+                              seg_meta(1000)];
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 2);
     }
@@ -147,24 +151,24 @@ mod tests {
     #[test]
     fn test_log_merge_policy_within_levels() {
         // multiple levels all get merged correctly
-        let test_input = vec![SegmentMeta::new(SegmentId::generate_random(), 10),
-                              SegmentMeta::new(SegmentId::generate_random(), 11),
-                              SegmentMeta::new(SegmentId::generate_random(), 12),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000),
-                              SegmentMeta::new(SegmentId::generate_random(), 1000)];
+        let test_input = vec![seg_meta(10),
+                              seg_meta(11),
+                              seg_meta(12),
+                              seg_meta(1000),
+                              seg_meta(1000),
+                              seg_meta(1000)];
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 2);
     }
     #[test]
     fn test_log_merge_policy_small_segments() {
         // multiple levels all get merged correctly
-        let test_input = vec![SegmentMeta::new(SegmentId::generate_random(), 1),
-                              SegmentMeta::new(SegmentId::generate_random(), 1),
-                              SegmentMeta::new(SegmentId::generate_random(), 1),
-                              SegmentMeta::new(SegmentId::generate_random(), 2),
-                              SegmentMeta::new(SegmentId::generate_random(), 2),
-                              SegmentMeta::new(SegmentId::generate_random(), 2)];
+        let test_input = vec![seg_meta(1),
+                              seg_meta(1),
+                              seg_meta(1),
+                              seg_meta(2),
+                              seg_meta(2),
+                              seg_meta(2)];
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 1);
     }
diff --git a/src/indexer/merge_policy.rs b/src/indexer/merge_policy.rs
index 22a767042..ecab510d7 100644
--- a/src/indexer/merge_policy.rs
+++ b/src/indexer/merge_policy.rs
@@ -13,7 +13,7 @@ pub struct MergeCandidate(pub Vec);
 /// 
 /// Every time a the list of segments changes, the segment updater
 /// asks the merge policy if some segments should be merged.
-pub trait MergePolicy: marker::Send + Debug {
+pub trait MergePolicy: marker::Send + marker::Sync + Debug {
     /// Given the list of segment metas, returns the list of merge candidates. 
     ///
     /// This call happens on the segment updater thread, and will block 
@@ -43,3 +43,38 @@ impl MergePolicy for NoMergePolicy {
     }
 }
 
+
+#[cfg(test)]
+pub mod tests {
+
+    use super::*;
+    use core::SegmentId;
+    use core::SegmentMeta;
+
+
+    /// Merge policy useful for test purposes.
+    ///
+    /// Everytime there is more than one segment,
+    /// it will suggest to merge them.
+    #[derive(Debug)]
+    pub struct MergeWheneverPossible;
+
+    impl MergePolicy for MergeWheneverPossible {
+        fn compute_merge_candidates(&self, segment_metas: &[SegmentMeta]) -> Vec {
+            let segment_ids = segment_metas
+                .iter()
+                .map(|segment_meta| segment_meta.id())
+                .collect::>();
+            if segment_ids.len() > 1 {
+                vec!(MergeCandidate(segment_ids))
+            }
+            else {
+                vec!()
+            }
+        }
+        
+        fn box_clone(&self) -> Box {
+            box MergeWheneverPossible
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/indexer/merger.rs b/src/indexer/merger.rs
index 740ae755b..bb0bb7ff7 100644
--- a/src/indexer/merger.rs
+++ b/src/indexer/merger.rs
@@ -1,27 +1,27 @@
-use Result;
+use {Error, Result};
 use core::SegmentReader;
 use core::Segment;
 use DocId;
 use core::SerializableSegment;
+use schema::FieldValue;
 use indexer::SegmentSerializer;
 use postings::PostingsSerializer;
+use fastfield::U32FastFieldReader;
+use itertools::Itertools;
 use postings::Postings;
 use postings::DocSet;
 use core::TermIterator;
+use fastfield::delete::DeleteBitSet;
 use schema::{Schema, Field};
 use fastfield::FastFieldSerializer;
 use store::StoreWriter;
-use postings::ChainedPostings;
-use postings::HasLen;
-use postings::OffsetPostings;
-use core::SegmentInfo;
 use std::cmp::{min, max};
-use std::iter;
+use common::allocate_vec;
 
 pub struct IndexMerger {
     schema: Schema,
     readers: Vec,
-    segment_info: SegmentInfo,
+    max_doc: u32,
 }
 
 
@@ -31,7 +31,9 @@ struct DeltaPositionComputer {
 
 impl DeltaPositionComputer {
     fn new() -> DeltaPositionComputer {
-        DeltaPositionComputer { buffer: iter::repeat(0u32).take(512).collect::>() }
+        DeltaPositionComputer { 
+            buffer: allocate_vec(512)
+        }
     }
 
     fn compute_delta_positions(&mut self, positions: &[u32]) -> &[u32] {
@@ -47,90 +49,157 @@ impl DeltaPositionComputer {
     }
 }
 
+
+fn compute_min_max_val(u32_reader: &U32FastFieldReader, max_doc: DocId, delete_bitset: &DeleteBitSet) -> Option<(u32, u32)> {
+    if max_doc == 0 {
+        None
+    }
+    else if !delete_bitset.has_deletes() {
+        // no deleted documents, 
+        // we can use the previous min_val, max_val.
+        Some((u32_reader.min_val(), u32_reader.max_val()))
+    }
+    else {
+        // some deleted documents,
+        // we need to recompute the max / min
+        (0..max_doc)
+            .filter(|doc_id| !delete_bitset.is_deleted(*doc_id))
+            .map(|doc_id| u32_reader.get(doc_id))
+            .minmax()
+            .into_option()
+    }
+}
+
+fn extract_fieldnorm_reader(segment_reader: &SegmentReader, field: Field) -> Option {
+    segment_reader.get_fieldnorms_reader(field)
+}
+
+fn extract_fast_field_reader(segment_reader: &SegmentReader, field: Field) -> Option {
+    segment_reader.get_fast_field_reader(field)
+}
+
 impl IndexMerger {
     pub fn open(schema: Schema, segments: &[Segment]) -> Result {
-        let mut readers = Vec::new();
-        let mut max_doc = 0;
+        let mut readers = vec!();
+        let mut max_doc: u32 = 0u32;
         for segment in segments {
-            let reader = try!(SegmentReader::open(segment.clone()));
-            max_doc += reader.max_doc();
-            readers.push(reader);
+            if segment.meta().num_docs() > 0 {
+                let reader = SegmentReader::open(segment.clone())?;
+                max_doc += reader.num_docs();
+                readers.push(reader);
+            }
         }
         Ok(IndexMerger {
             schema: schema,
             readers: readers,
-            segment_info: SegmentInfo { max_doc: max_doc },
+            max_doc: max_doc,
         })
     }
 
-
-    fn write_fieldnorms(&self, fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
-        // TODO make sure that works even if the field is never here.
-        for field in self.schema
+    fn write_fieldnorms(&self,
+        fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
+        let fieldnorm_fastfields: Vec = self.schema
                          .fields()
                          .iter()
                          .enumerate()
                          .filter(|&(_, field_entry)| field_entry.is_indexed())
-                         .map(|(field_id, _)| Field(field_id as u8)) {
-            let mut u32_readers = Vec::new();
-            let mut min_val = u32::min_value();
-            let mut max_val = 0;
-            for reader in &self.readers {
-                let u32_reader = try!(reader.get_fieldnorms_reader(field));
-                min_val = min(min_val, u32_reader.min_val());
-                max_val = max(max_val, u32_reader.max_val());
-                u32_readers.push((reader.max_doc(), u32_reader));
-            }
-            try!(fast_field_serializer.new_u32_fast_field(field, min_val, max_val));
-            for (max_doc, u32_reader) in u32_readers {
-                for doc_id in 0..max_doc {
-                    let val = u32_reader.get(doc_id);
-                    try!(fast_field_serializer.add_val(val));
-                }
-            }
-            try!(fast_field_serializer.close_field());
-        }
-        Ok(())
+                         .map(|(field_id, _)| Field(field_id as u8))
+                         .collect();
+        self.generic_write_fast_field(fieldnorm_fastfields, &extract_fieldnorm_reader, fast_field_serializer)
     }
 
     fn write_fast_fields(&self, fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
-        for field in self.schema
+        let fast_fields: Vec = self.schema
                          .fields()
                          .iter()
                          .enumerate()
                          .filter(|&(_, field_entry)| field_entry.is_u32_fast())
-                         .map(|(field_id, _)| Field(field_id as u8)) {
-            let mut u32_readers = Vec::new();
+                         .map(|(field_id, _)| Field(field_id as u8))
+                         .collect();
+        self.generic_write_fast_field(fast_fields, &extract_fast_field_reader, fast_field_serializer)
+    }
+
+
+    // used both to merge field norms and regular u32 fast fields.
+    fn generic_write_fast_field(&self,
+        fields: Vec,
+        field_reader_extractor: &Fn(&SegmentReader, Field) -> Option,
+        fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
+        
+        for field in fields {
+            
+            let mut u32_readers = vec!();
             let mut min_val = u32::max_value();
             let mut max_val = u32::min_value();
+            
             for reader in &self.readers {
-                let u32_reader = try!(reader.get_fast_field_reader(field));
-                min_val = min(min_val, u32_reader.min_val());
-                max_val = max(max_val, u32_reader.max_val());
-                u32_readers.push((reader.max_doc(), u32_reader));
+                match field_reader_extractor(reader, field) {
+                    Some(u32_reader) => {
+                        if let Some((seg_min_val, seg_max_val)) = compute_min_max_val(&u32_reader, reader.max_doc(), reader.delete_bitset()) {
+                            // the segment has some non-deleted documents
+                            min_val = min(min_val, seg_min_val);
+                            max_val = max(max_val, seg_max_val);
+                            u32_readers.push((reader.max_doc(), u32_reader, reader.delete_bitset()));
+                        }        
+                    }
+                    None => {
+                        let error_msg = format!("Failed to find a u32_reader for field {:?}", field);
+                        error!("{}", error_msg);
+                        return Err(Error::SchemaError(error_msg))
+                    }
+                }
+                
             }
+
+            if u32_readers.is_empty() {
+                // we have actually zero documents.
+                min_val = 0;
+                max_val = 0;
+            }
+
+            assert!(min_val <= max_val);
+            
             try!(fast_field_serializer.new_u32_fast_field(field, min_val, max_val));
-            for (max_doc, u32_reader) in u32_readers {
+            for (max_doc, u32_reader, delete_bitset) in u32_readers {
                 for doc_id in 0..max_doc {
-                    let val = u32_reader.get(doc_id);
-                    try!(fast_field_serializer.add_val(val));
+                    if !delete_bitset.is_deleted(doc_id) {
+                        let val = u32_reader.get(doc_id);
+                        try!(fast_field_serializer.add_val(val));
+                    }
                 }
             }
+
             try!(fast_field_serializer.close_field());
         }
         Ok(())
     }
 
-    fn write_postings(&self, postings_serializer: &mut PostingsSerializer) -> Result<()> {
+    fn write_postings(
+            &self,
+            postings_serializer: &mut PostingsSerializer) -> Result<()> {
+        
         let mut merged_terms = TermIterator::from(&self.readers[..]);
         let mut delta_position_computer = DeltaPositionComputer::new();
-        let mut offsets: Vec = Vec::new();
+        
         let mut max_doc = 0;
-        for reader in &self.readers {
-            offsets.push(max_doc);
-            max_doc += reader.max_doc();
-        }
 
+        // map from segment doc ids to the resulting merged segment doc id.
+        let mut merged_doc_id_map: Vec>> = Vec::with_capacity(self.readers.len());
+        
+        for reader in &self.readers {
+            let mut segment_local_map = Vec::with_capacity(reader.max_doc() as usize);
+            for doc_id in 0..reader.max_doc() {
+                if reader.is_deleted(doc_id) {
+                    segment_local_map.push(None);
+                }
+                else {
+                    segment_local_map.push(Some(max_doc));
+                    max_doc += 1u32;
+                }
+            }
+            merged_doc_id_map.push(segment_local_map);
+        }
+        
         while merged_terms.advance() {
             // Create the total list of doc ids
             // by stacking the doc ids from the different segment.
@@ -142,41 +211,66 @@ impl IndexMerger {
             // - Segment 2's doc ids become  [seg0.max_doc + seg1.max_doc, seg0.max_doc + seg1.max_doc + seg2.max_doc]
             // ...
             let term = merged_terms.term();
-            let mut merged_postings =
-                ChainedPostings::from(
-                    merged_terms
-                        .segment_ords()
-                        .iter()
-                        .cloned()
-                        .flat_map(|segment_ord| {
-                            let offset = offsets[segment_ord];
-                            self.readers[segment_ord]
-                                .read_postings_all_info(&term)
-                                .map(|segment_postings| OffsetPostings::new(segment_postings, offset))
-                        })
-                        .collect::>()
-            );
+            let mut term_written = false;
+            let segment_postings = merged_terms
+                    .segment_ords()
+                    .iter()
+                    .cloned()
+                    .flat_map(|segment_ord| {
+                        self.readers[segment_ord]
+                            .read_postings_all_info(&term)
+                            .map(|segment_postings| (segment_ord, segment_postings))
+                    })
+                    .collect::>();
 
-            // We can now serialize this postings, by pushing each document to the
-            // postings serializer.
-            try!(postings_serializer.new_term(&term, merged_postings.len() as DocId));
-            while merged_postings.advance() {
-                let delta_positions: &[u32] =
-                    delta_position_computer.compute_delta_positions(merged_postings.positions());
-                try!(postings_serializer.write_doc(merged_postings.doc(),
-                                                   merged_postings.term_freq(),
-                                                   delta_positions));
+            // We can remove the term if all documents which
+            // contained it have been deleted.
+            if segment_postings.len() > 0 {
+                
+                // We can now serialize this postings, by pushing each document to the
+                // postings serializer.                
+                
+                for (segment_ord, mut segment_postings) in segment_postings {
+                    let old_to_new_doc_id = &merged_doc_id_map[segment_ord];
+                    while segment_postings.advance() {
+                        if let Some(remapped_doc_id) = old_to_new_doc_id[segment_postings.doc() as usize] {
+                            if !term_written {
+                                // we make sure to only write the term iff
+                                // there is at least one document.
+                                postings_serializer.new_term(&term)?;
+                                term_written = true;
+                            }
+                            let delta_positions: &[u32] =
+                                delta_position_computer.compute_delta_positions(segment_postings.positions());
+                            try!(postings_serializer.write_doc(
+                                    remapped_doc_id,
+                                    segment_postings.term_freq(),
+                                    delta_positions));
+                        }
+                    }
+                }
+
+                if term_written {
+                    try!(postings_serializer.close_term());
+                }
             }
-            try!(postings_serializer.close_term());
+            
         }
-
         Ok(())
     }
 
     fn write_storable_fields(&self, store_writer: &mut StoreWriter) -> Result<()> {
         for reader in &self.readers {
             let store_reader = reader.get_store_reader();
-            try!(store_writer.stack_reader(store_reader));
+            for doc_id in 0..reader.max_doc() {
+                if !reader.is_deleted(doc_id) {
+                    let doc = try!(store_reader.get(doc_id));
+                    let field_values: Vec<&FieldValue> = doc.field_values()
+                        .iter()
+                        .collect();
+                    try!(store_writer.store(&field_values));
+                }
+            }   
         }
         Ok(())
     }
@@ -188,9 +282,8 @@ impl SerializableSegment for IndexMerger {
         try!(self.write_fieldnorms(serializer.get_fieldnorms_serializer()));
         try!(self.write_fast_fields(serializer.get_fast_field_serializer()));
         try!(self.write_storable_fields(serializer.get_store_writer()));
-        try!(serializer.write_segment_info(&self.segment_info));
         try!(serializer.close());
-        Ok(self.segment_info.max_doc)
+        Ok(self.max_doc)
     }
 }
 
@@ -199,15 +292,20 @@ mod tests {
     use schema;
     use schema::Document;
     use schema::Term;
+    use query::TermQuery;
+    use schema::{Field, FieldValue};
     use core::Index;
+    use Searcher;
     use DocAddress;
     use collector::tests::FastFieldTestCollector;
     use collector::tests::TestCollector;
     use query::BooleanQuery;
+    use postings::SegmentPostingsOption;
     use schema::TextIndexingOptions;
+    use futures::Future;
 
     #[test]
-    fn test_index_merger() {
+    fn test_index_merger_no_deletes() {
         let mut schema_builder = schema::SchemaBuilder::default();
         let text_fieldtype = schema::TextOptions::default()
                                  .set_indexing_options(TextIndexingOptions::TokenizedWithFreq)
@@ -225,21 +323,21 @@ mod tests {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "af b");
                     doc.add_u32(score_field, 3);
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "a b c");
                     doc.add_u32(score_field, 5);
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "a b c d");
                     doc.add_u32(score_field, 7);
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
-                index_writer.commit().unwrap();
+                index_writer.commit().expect("committed");
             }
 
             {
@@ -248,23 +346,27 @@ mod tests {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "af b");
                     doc.add_u32(score_field, 11);
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 {
                     let mut doc = Document::default();
                     doc.add_text(text_field, "a b c g");
                     doc.add_u32(score_field, 13);
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
-                index_writer.commit().unwrap();
+                index_writer.commit().expect("Commit failed");
             }
         }
         {
-            let segments = index.searchable_segments();
+            let segment_ids = index.searchable_segment_ids().expect("Searchable segments failed.");
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
-            index_writer.merge(&segments).unwrap();
+            index_writer.merge(&segment_ids)
+                        .wait()
+                        .expect("Merging failed");
+            index_writer.wait_merging_threads().unwrap();
         }
         {
+            index.load_searchers().unwrap();
             let searcher = index.searcher();
             let get_doc_ids = |terms: Vec| {
                 let mut collector = TestCollector::default();
@@ -307,11 +409,192 @@ mod tests {
                     let query = BooleanQuery::new_multiterms_query(terms);
                     let mut collector = FastFieldTestCollector::for_field(score_field);
                     assert!(searcher.search(&query, &mut collector).is_ok());
-                    collector.vals().clone()
+                    collector.vals()
                 };
                 assert_eq!(get_fast_vals(vec![Term::from_field_text(text_field, "a")]),
                            vec!(5, 7, 13,));
             }
         }
     }
+
+    fn search_term(searcher: &Searcher, term: Term) ->  Vec {
+        let mut collector = FastFieldTestCollector::for_field(Field(1));
+        let term_query = TermQuery::new(term, SegmentPostingsOption::NoFreq);
+        searcher.search(&term_query, &mut collector).unwrap();
+        collector.vals()
+    }
+
+    #[test]
+    fn test_index_merger_with_deletes() {
+        let mut schema_builder = schema::SchemaBuilder::default();
+        let text_fieldtype = schema::TextOptions
+            ::default()
+            .set_indexing_options(TextIndexingOptions::TokenizedWithFreq)
+            .set_stored();
+        let text_field = schema_builder.add_text_field("text", text_fieldtype);
+        let score_fieldtype = schema::U32Options::default().set_fast();
+        let score_field = schema_builder.add_u32_field("score", score_fieldtype);
+        let index = Index::create_in_ram(schema_builder.build());
+        let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            
+        {   // a first commit
+            index_writer.add_document(
+                doc!(
+                    text_field => "a b d",
+                    score_field => 1
+                ));
+            index_writer.add_document(
+                doc!(
+                    text_field => "b c",
+                    score_field => 2
+                ));
+            index_writer.delete_term(Term::from_field_text(text_field, "c"));
+            index_writer.add_document(
+                doc!(
+                    text_field => "c d",
+                    score_field => 3
+                ));
+            index_writer.commit().expect("committed");
+            index.load_searchers().unwrap();
+            let ref searcher = *index.searcher();
+            assert_eq!(searcher.num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "a")), vec!(1));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "b")), vec!(1));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "c")), vec!(3));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "d")), vec!(1, 3));
+        }
+        {   // a second commit
+            index_writer.add_document(
+                doc!(
+                    text_field => "a d e",
+                    score_field => 4_000
+                ));
+            index_writer.add_document(
+                doc!(
+                    text_field => "e f",
+                    score_field => 5_000
+                ));
+            index_writer.delete_term(Term::from_field_text(text_field, "a"));
+            index_writer.delete_term(Term::from_field_text(text_field, "f"));
+            index_writer.add_document(
+                doc!(
+                    text_field => "f g",
+                    score_field => 6_000
+                ));
+            index_writer.add_document(
+                doc!(
+                    text_field => "g h",
+                    score_field => 7_000
+                ));
+            index_writer.commit().expect("committed");
+            index.load_searchers().unwrap();
+            let searcher = index.searcher();
+
+            assert_eq!(searcher.segment_readers().len(), 2);
+            assert_eq!(searcher.num_docs(), 3);
+            assert_eq!(searcher.segment_readers()[0].num_docs(), 1);
+            assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
+            assert_eq!(searcher.segment_readers()[1].num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[1].max_doc(), 4);
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "a")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "b")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "c")), vec!(3));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "d")), vec!(3));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "e")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "f")), vec!(6_000));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "g")), vec!(6_000, 7_000));
+            
+            let score_field_reader = searcher.segment_reader(0).get_fast_field_reader(score_field).unwrap();
+            assert_eq!(score_field_reader.min_val(), 1);
+            assert_eq!(score_field_reader.max_val(), 3);
+
+            let score_field_reader = searcher.segment_reader(1).get_fast_field_reader(score_field).unwrap();
+            assert_eq!(score_field_reader.min_val(), 4000);
+            assert_eq!(score_field_reader.max_val(), 7000);
+        }
+        {   // merging the segments
+            let segment_ids = index.searchable_segment_ids().expect("Searchable segments failed.");
+            index_writer.merge(&segment_ids)
+                        .wait()
+                        .expect("Merging failed");
+            index.load_searchers().unwrap();
+            let ref searcher = *index.searcher();
+            assert_eq!(searcher.segment_readers().len(), 1);
+            assert_eq!(searcher.num_docs(), 3);
+            assert_eq!(searcher.segment_readers()[0].num_docs(), 3);
+            assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "a")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "b")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "c")), vec!(3));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "d")), vec!(3));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "e")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "f")), vec!(6_000));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "g")), vec!(6_000, 7_000));
+            let score_field_reader = searcher.segment_reader(0).get_fast_field_reader(score_field).unwrap();
+            assert_eq!(score_field_reader.min_val(), 3);
+            assert_eq!(score_field_reader.max_val(), 7000);
+        }
+        {   
+            // test a commit with only deletes
+            index_writer.delete_term(Term::from_field_text(text_field, "c"));
+            index_writer.commit().unwrap();
+        
+            index.load_searchers().unwrap();
+            let ref searcher = *index.searcher();
+            assert_eq!(searcher.segment_readers().len(), 1);
+            assert_eq!(searcher.num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "a")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "b")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "c")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "d")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "e")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "f")), vec!(6_000));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "g")), vec!(6_000, 7_000));
+            let score_field_reader = searcher.segment_reader(0).get_fast_field_reader(score_field).unwrap();
+            assert_eq!(score_field_reader.min_val(), 3);
+            assert_eq!(score_field_reader.max_val(), 7000);
+        }
+        {   // Test merging a single segment in order to remove deletes.
+            let segment_ids = index.searchable_segment_ids().expect("Searchable segments failed.");
+            index_writer.merge(&segment_ids)
+                        .wait()
+                        .expect("Merging failed");
+            index.load_searchers().unwrap();
+
+            let ref searcher = *index.searcher();
+            assert_eq!(searcher.segment_readers().len(), 1);
+            assert_eq!(searcher.num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
+            assert_eq!(searcher.segment_readers()[0].max_doc(), 2);
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "a")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "b")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "c")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "d")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "e")), vec!());
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "f")), vec!(6_000));
+            assert_eq!(search_term(&searcher, Term::from_field_text(text_field, "g")), vec!(6_000, 7_000));
+            let score_field_reader = searcher.segment_reader(0).get_fast_field_reader(score_field).unwrap();
+            assert_eq!(score_field_reader.min_val(), 6000);
+            assert_eq!(score_field_reader.max_val(), 7000);
+        }
+
+        {   // Test removing all docs
+            index_writer.delete_term(Term::from_field_text(text_field, "g"));
+            let segment_ids = index.searchable_segment_ids().expect("Searchable segments failed.");
+            index_writer.merge(&segment_ids)
+                        .wait()
+                        .expect("Merging failed");
+            index.load_searchers().unwrap();
+
+            let ref searcher = *index.searcher();
+            assert_eq!(searcher.segment_readers().len(), 1);
+            assert_eq!(searcher.num_docs(), 0);
+        }
+        
+        
+    }
 }
diff --git a/src/indexer/mod.rs b/src/indexer/mod.rs
index c71c07fb4..4dcd9fe12 100644
--- a/src/indexer/mod.rs
+++ b/src/indexer/mod.rs
@@ -1,5 +1,4 @@
-
-mod index_writer;
+pub mod index_writer;
 pub mod segment_serializer;
 pub mod merger;
 mod merge_policy;
@@ -7,9 +6,15 @@ mod log_merge_policy;
 mod segment_register;
 mod segment_writer;
 mod segment_manager;
+pub mod delete_queue;
 pub mod segment_updater;
 mod directory_lock;
+mod segment_entry;
+mod doc_opstamp_mapping;
+pub mod operation;
+mod stamper;
 
+pub use self::segment_entry::{SegmentEntry, SegmentState};
 pub use self::segment_serializer::SegmentSerializer;
 pub use self::segment_writer::SegmentWriter;
 pub use self::index_writer::IndexWriter;
@@ -17,6 +22,5 @@ pub use self::log_merge_policy::LogMergePolicy;
 pub use self::merge_policy::{NoMergePolicy, MergeCandidate, MergePolicy};
 pub use self::segment_manager::SegmentManager;
 
-
 /// Alias for the default merge policy, which is the LogMergePolicy.
 pub type DefaultMergePolicy = LogMergePolicy;
diff --git a/src/indexer/operation.rs b/src/indexer/operation.rs
new file mode 100644
index 000000000..ecdc2d827
--- /dev/null
+++ b/src/indexer/operation.rs
@@ -0,0 +1,17 @@
+use schema::Document;
+use schema::Term;
+
+
+/// Timestamped Delete operation.
+#[derive(Clone, Eq, PartialEq, Debug)]
+pub struct DeleteOperation {
+    pub opstamp: u64,
+    pub term: Term,
+}
+
+/// Timestamped Add operation.
+#[derive(Eq, PartialEq, Debug)]
+pub struct AddOperation {
+    pub opstamp: u64,
+    pub document: Document,
+}
diff --git a/src/indexer/segment_entry.rs b/src/indexer/segment_entry.rs
new file mode 100644
index 000000000..86673d517
--- /dev/null
+++ b/src/indexer/segment_entry.rs
@@ -0,0 +1,129 @@
+use core::SegmentMeta;
+use bit_set::BitSet;
+use indexer::delete_queue::DeleteCursor;
+use core::SegmentId;
+use std::fmt;
+
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum SegmentState {
+    Ready,
+    InMerge,        
+}
+
+impl SegmentState {
+    pub fn letter_code(&self,) -> char {
+        match *self {
+            SegmentState::InMerge => 'M',
+            SegmentState::Ready => 'R',
+        }
+    }
+}
+
+
+/// A segment entry describes the state of 
+/// a given segment, at a given instant.
+///
+/// In addition to segment meta,
+/// it contains a few transient states
+/// - state expresses whether the segment is already in the 
+/// middle of a merge
+/// - delete_bitset is a bitset describing
+/// documents that were deleted during the commit
+/// itself.
+/// - Delete cursor, is the position in the delete queue.
+/// Deletes happening before the cursor are reflected either
+/// in the .del file or in the delete_bitset.
+#[derive(Clone)]
+pub struct SegmentEntry {
+    meta: SegmentMeta,
+    state: SegmentState,
+    delete_bitset: Option,
+    delete_cursor: DeleteCursor,
+
+}
+
+impl SegmentEntry {
+
+
+    /// Create a new `SegmentEntry`
+    pub fn new(segment_meta: SegmentMeta, 
+               delete_cursor: DeleteCursor,
+               delete_bitset: Option) -> SegmentEntry {
+        SegmentEntry {
+            meta: segment_meta,
+            state: SegmentState::Ready,
+            delete_bitset: delete_bitset,
+            delete_cursor: delete_cursor,
+        }
+    }
+
+
+    /// Return a reference to the segment entry deleted bitset.
+    ///
+    /// `DocId` in this bitset are flagged as deleted.
+    pub fn delete_bitset(&self,) -> Option<&BitSet> {
+        self.delete_bitset.as_ref()
+    }
+
+    /// Set the `SegmentMeta` for this segment.
+    pub fn set_meta(&mut self, segment_meta: SegmentMeta) {
+        self.meta = segment_meta;
+    }
+
+
+    /// Return a reference to the segment_entry's delete cursor
+    pub fn delete_cursor(&mut self) -> &mut DeleteCursor {
+        &mut self.delete_cursor
+    }
+
+    /// Return the `SegmentEntry`. 
+    ///
+    /// The state describes whether the segment is available for
+    /// a merge or not.
+    pub fn state(&self) -> SegmentState {
+        self.state
+    }
+
+    /// Returns the segment id.
+    pub fn segment_id(&self) -> SegmentId {
+        self.meta.id()
+    }
+    
+
+    /// Accessor to the `SegmentMeta`
+    pub fn meta(&self) -> &SegmentMeta {
+        &self.meta
+    }
+
+
+    /// Mark the `SegmentEntry` as in merge.
+    ///
+    /// Only segments that are not already 
+    /// in a merge are elligible for future merge.
+    pub fn start_merge(&mut self,) {
+        self.state = SegmentState::InMerge;
+    }
+
+    /// Cancel a merge
+    ///
+    /// If a merge fails, it is important to switch
+    /// the segment back to a idle state, so that it
+    /// may be elligible for future merges.
+    pub fn cancel_merge(&mut self,) {
+        self.state = SegmentState::Ready;
+    }
+
+
+    /// Returns true iff a segment should
+    /// be considered for a merge.
+    pub fn is_ready(&self,) -> bool {
+        self.state == SegmentState::Ready
+    }
+}
+
+impl fmt::Debug for SegmentEntry {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "SegmentEntry({:?}, {:?})", self.meta, self.state)
+    }
+}
diff --git a/src/indexer/segment_manager.rs b/src/indexer/segment_manager.rs
index 3a41adc25..66f6fe569 100644
--- a/src/indexer/segment_manager.rs
+++ b/src/indexer/segment_manager.rs
@@ -1,33 +1,22 @@
 use super::segment_register::SegmentRegister;
 use std::sync::RwLock;
 use core::SegmentMeta;
+use core::{META_FILEPATH, LOCKFILE_FILEPATH};
 use core::SegmentId;
+use indexer::SegmentEntry;
+use std::path::PathBuf;
+use std::collections::hash_set::HashSet;
 use std::sync::{RwLockReadGuard, RwLockWriteGuard};
 use std::fmt::{self, Debug, Formatter};
-use std::sync::atomic::{AtomicUsize, Ordering};
+use indexer::delete_queue::DeleteCursor;
 
+#[derive(Default)]
 struct SegmentRegisters {
-    docstamp: u64,
     uncommitted: SegmentRegister,
     committed: SegmentRegister,
+    writing: HashSet,    
 }
 
-#[derive(Eq, PartialEq)]
-pub enum CommitState {
-    Committed,
-    Uncommitted,
-    Missing,
-}
-
-impl Default for SegmentRegisters {
-    fn default() -> SegmentRegisters {
-        SegmentRegisters {
-            docstamp: 0u64,
-            uncommitted: SegmentRegister::default(),
-            committed: SegmentRegister::default()
-        }
-    }
-}
 
 
 /// The segment manager stores the list of segments
@@ -35,14 +24,9 @@ impl Default for SegmentRegisters {
 ///
 /// It guarantees the atomicity of the 
 /// changes (merges especially)
+#[derive(Default)]
 pub struct SegmentManager {
     registers: RwLock,
-    // generation  is an ever increasing counter that 
-    // is incremented whenever we modify 
-    // the segment manager. It can be useful for debugging
-    // purposes, and it also acts as a "dirty" marker,
-    // to detect when the `meta.json` should be written.
-    generation: AtomicUsize, 
 }
 
 impl Debug for SegmentManager {
@@ -52,47 +36,73 @@ impl Debug for SegmentManager {
     }
 }
 
-
-/// Returns the `SegmentMeta`s for (committed segment, uncommitted segments).
-/// The result is consistent with other transactions.
-///
-/// For instance, a segment will not appear in both committed and uncommitted 
-/// segments
-pub fn get_segment_ready_for_commit(segment_manager: &SegmentManager,) -> (Vec, Vec) {
+pub fn get_mergeable_segments(segment_manager: &SegmentManager,) -> (Vec, Vec) {
     let registers_lock = segment_manager.read();
-    (registers_lock.committed.get_segment_ready_for_commit(),
-     registers_lock.uncommitted.get_segment_ready_for_commit())
+    (registers_lock.committed.get_mergeable_segments(),
+     registers_lock.uncommitted.get_mergeable_segments())
 }
 
 impl SegmentManager {
     
-    /// Returns whether a segment is committed, uncommitted or missing.
-    pub fn is_committed(&self, segment_id: SegmentId) -> CommitState {
-        let lock = self.read();
-        if lock.uncommitted.contains(segment_id) {
-            CommitState::Uncommitted
+    pub fn from_segments(segment_metas: Vec, delete_cursor: DeleteCursor) -> SegmentManager {
+        SegmentManager {
+            registers: RwLock::new(SegmentRegisters {
+                uncommitted: SegmentRegister::default(),
+                committed: SegmentRegister::new(segment_metas, delete_cursor),
+                writing: HashSet::new(),
+            }),
         }
-        else if lock.committed.contains(segment_id) {
-            CommitState::Committed
-        }
-        else {
-            CommitState::Missing
-        }
-    }
-    
-    pub fn docstamp(&self,) -> u64 {
-        self.read().docstamp
     }
 
-    pub fn from_segments(segment_metas: Vec) -> SegmentManager {
-        SegmentManager {
-            registers: RwLock::new( SegmentRegisters {
-                docstamp: 0u64, // TODO put the actual value
-                uncommitted: SegmentRegister::default(),
-                committed: SegmentRegister::from(segment_metas),
-            }),
-            generation: AtomicUsize::default(),
+    /// Returns all of the segment entries (committed or uncommitted)
+    pub fn segment_entries(&self,) -> Vec {
+        let mut segment_entries = self.read()
+            .uncommitted
+            .segment_entries();
+        segment_entries.extend(
+            self.read()
+            .committed
+            .segment_entries()
+        );
+        segment_entries
+    }
+
+    /// Returns the overall number of segments in the `SegmentManager`
+    pub fn num_segments(&self,) -> usize {
+        let registers_lock = self.read();
+        registers_lock.committed.len() + registers_lock.uncommitted.len()
+    }
+
+    pub fn list_files(&self) -> HashSet {
+        let registers_lock = self.read();
+        let mut files = HashSet::new();
+        files.insert(META_FILEPATH.clone());
+        files.insert(LOCKFILE_FILEPATH.clone());
+                
+        let segment_metas: Vec =
+            registers_lock.committed
+                .get_all_segments()
+                .into_iter()
+                .chain(registers_lock.uncommitted
+                    .get_all_segments()
+                    .into_iter())
+                .chain(registers_lock.writing
+                    .iter()
+                    .cloned()
+                    .map(SegmentMeta::new))
+                .collect();
+        for segment_meta in segment_metas {
+            files.extend(segment_meta.list_files());
         }
+        files
+    }
+
+    pub fn segment_entry(&self, segment_id: &SegmentId) -> Option {
+        let registers = self.read();
+        registers
+            .committed
+            .segment_entry(segment_id)
+            .or_else(|| registers.uncommitted.segment_entry(segment_id))        
     }
 
     // Lock poisoning should never happen :
@@ -103,36 +113,16 @@ impl SegmentManager {
     }
 
     fn write(&self,) -> RwLockWriteGuard {
-        self.generation.fetch_add(1, Ordering::Release);
         self.registers.write().expect("Failed to acquire write lock on SegmentManager.")
     }
 
-    pub fn generation(&self,) -> usize {
-        self.generation.load(Ordering::Acquire)
-    }
-
-    /// Removes all of the uncommitted segments
-    /// and returns them.
-    pub fn rollback(&self,) -> Vec {
+    pub fn commit(&self, segment_entries: Vec) {
         let mut registers_lock = self.write();
-        let segment_ids = registers_lock.uncommitted.segment_ids();
+        registers_lock.committed.clear();
         registers_lock.uncommitted.clear();
-        segment_ids
-    }
-
-    pub fn commit(&self, docstamp: u64) {
-        let mut registers_lock = self.write();
-        let segment_entries = registers_lock.uncommitted.segment_entries();
         for segment_entry in segment_entries {
             registers_lock.committed.add_segment_entry(segment_entry);
         }
-        registers_lock.docstamp = docstamp;
-        registers_lock.uncommitted.clear();    
-    }
-    
-    pub fn add_segment(&self, segment_meta: SegmentMeta) {
-        let mut registers_lock = self.write();
-        registers_lock.uncommitted.add_segment(segment_meta);
     }
     
     pub fn start_merge(&self, segment_ids: &[SegmentId]) {
@@ -147,34 +137,86 @@ impl SegmentManager {
                 registers_lock.committed.start_merge(segment_id);
             }
         }
+        else {
+            error!("Merge operation sent for segments that are not all uncommited or commited.");
+        }
     }
-    
-    pub fn end_merge(&self, merged_segment_ids: &[SegmentId], merged_segment_meta: &SegmentMeta) {
+
+
+    pub fn cancel_merge(&self,
+            before_merge_segment_ids: &[SegmentId],
+            after_merge_segment_id: SegmentId) {
+        
         let mut registers_lock = self.write();
-        if registers_lock.uncommitted.contains_all(merged_segment_ids) {
-            for segment_id in merged_segment_ids {
-                registers_lock.uncommitted.remove_segment(segment_id);
+        
+        // we mark all segments are ready for merge.
+        {
+            let target_segment_register: &mut SegmentRegister;
+            target_segment_register = {
+                if registers_lock.uncommitted.contains_all(&before_merge_segment_ids) {
+                    &mut registers_lock.uncommitted
+                }
+                else if registers_lock.committed.contains_all(&before_merge_segment_ids) {
+                    &mut registers_lock.committed
+                }
+                else {
+                    warn!("couldn't find segment in SegmentManager");
+                    return;
+                }
+            };
+            for segment_id in before_merge_segment_ids {
+                target_segment_register.cancel_merge(segment_id);
             }
-            registers_lock.uncommitted.add_segment(merged_segment_meta.clone());
-        }
-        else if registers_lock.committed.contains_all(merged_segment_ids) {
-            for segment_id in merged_segment_ids {
-                registers_lock.committed.remove_segment(segment_id);
-            }
-            registers_lock.committed.add_segment(merged_segment_meta.clone());
-        } else {
-            warn!("couldn't find segment in SegmentManager");
         }
+
+        // ... and we make sure the target segment entry
+        // can be garbage collected.
+        registers_lock.writing.remove(&after_merge_segment_id);
+        
+    }
+
+
+    pub fn write_segment(&self, segment_id: SegmentId) {
+        let mut registers_lock = self.write();
+        registers_lock.writing.insert(segment_id);
+    }
+
+    pub fn add_segment(&self, segment_entry: SegmentEntry) {
+        let mut registers_lock = self.write();
+        registers_lock.writing.remove(&segment_entry.segment_id());
+        registers_lock.uncommitted.add_segment_entry(segment_entry);
     }
     
-    pub fn committed_segments(&self,) -> Vec {
-        let registers_lock = self.read();
-        registers_lock.committed.segment_ids()
+    pub fn end_merge(&self,
+            before_merge_segment_ids: &[SegmentId],
+            after_merge_segment_entry: SegmentEntry) {
+        
+        let mut registers_lock = self.write();
+        registers_lock.writing.remove(&after_merge_segment_entry.segment_id());
+        
+        let mut target_register: &mut SegmentRegister = {
+            if registers_lock.uncommitted.contains_all(&before_merge_segment_ids) {
+                &mut registers_lock.uncommitted
+            }
+            else if registers_lock.committed.contains_all(&before_merge_segment_ids) {
+                &mut registers_lock.committed
+            } else {
+                warn!("couldn't find segment in SegmentManager");
+                return;
+            }
+        };
+        for segment_id in before_merge_segment_ids {
+            target_register.remove_segment(segment_id);
+        }
+        target_register.add_segment_entry(after_merge_segment_entry);
+
+        
+
+        
     }
-    
-    pub fn segment_metas(&self,) -> (Vec, Vec) {
+
+    pub fn committed_segment_metas(&self,) -> Vec {
         let registers_lock = self.read();
-        (registers_lock.committed.segment_metas(), registers_lock.uncommitted.segment_metas())
+        registers_lock.committed.segment_metas()
     }
 }
-
diff --git a/src/indexer/segment_register.rs b/src/indexer/segment_register.rs
index 5718a6228..f8f7c7d64 100644
--- a/src/indexer/segment_register.rs
+++ b/src/indexer/segment_register.rs
@@ -3,39 +3,8 @@ use std::collections::HashMap;
 use core::SegmentMeta;
 use std::fmt;
 use std::fmt::{Debug, Formatter};
-
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub enum SegmentState {
-    Ready,
-    InMerge,    
-}
-
-impl SegmentState {
-    fn letter_code(&self,) -> char {
-        match *self {
-            SegmentState::InMerge => 'M',
-            SegmentState::Ready => 'R',
-        }
-    }
-}
-
-#[derive(Clone)]
-pub struct SegmentEntry {
-    meta: SegmentMeta,
-    state: SegmentState,
-}
-
-impl SegmentEntry {
-    fn start_merge(&mut self,) {
-        self.state = SegmentState::InMerge;
-    }
-
-    fn is_ready(&self,) -> bool {
-        self.state == SegmentState::Ready
-    }
-}
-
-
+use indexer::segment_entry::SegmentEntry;
+use indexer::delete_queue::DeleteCursor;
 
 /// The segment register keeps track
 /// of the list of segment, their size as well
@@ -45,36 +14,50 @@ impl SegmentEntry {
 /// segments that are currently searchable,
 /// and by the index merger to identify 
 /// merge candidates.
+#[derive(Default)]
 pub struct SegmentRegister {
     segment_states: HashMap, 
 }
 
+
 impl Debug for SegmentRegister {
     fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
         try!(write!(f, "SegmentRegister("));
         for (k, v) in &self.segment_states {
-            try!(write!(f, "{}:{}, ", k.short_uuid_string(), v.state.letter_code()));
+            try!(write!(f, "{}:{}, ", k.short_uuid_string(), v.state().letter_code()));
         }
         try!(write!(f, ")"));
         Ok(())
     }
 }
 
+
 impl SegmentRegister {
     
     pub fn clear(&mut self,) {
         self.segment_states.clear();
     }
-    
-    pub fn get_segment_ready_for_commit(&self,) -> Vec {
+
+    pub fn len(&self) -> usize {
+        self.segment_states.len()
+    }
+
+    pub fn get_all_segments(&self,) -> Vec {
         self.segment_states
             .values()
-            .filter(|segment_entry| segment_entry.is_ready())
-            .map(|segment_entry| segment_entry.meta.clone())
+            .map(|segment_entry| segment_entry.meta().clone())
             .collect()
     }
     
-    pub fn segment_entries(&self,) -> Vec{
+    pub fn get_mergeable_segments(&self,) -> Vec {
+        self.segment_states
+            .values()
+            .filter(|segment_entry| segment_entry.is_ready())
+            .map(|segment_entry| segment_entry.meta().clone())
+            .collect()
+    }
+    
+    pub fn segment_entries(&self,) -> Vec {
         self.segment_states
             .values()
             .cloned()
@@ -84,31 +67,18 @@ impl SegmentRegister {
     pub fn segment_metas(&self,) -> Vec {
         let mut segment_ids: Vec = self.segment_states
             .values()
-            .map(|segment_entry| segment_entry.meta.clone())
+            .map(|segment_entry| segment_entry.meta().clone())
             .collect();
-        segment_ids.sort_by_key(|meta| meta.segment_id);
+        segment_ids.sort_by_key(|meta| meta.id());
         segment_ids
     }
     
-    pub fn segment_ids(&self,) -> Vec {
-        self.segment_metas()
-            .into_iter()
-            .map(|segment_meta| segment_meta.segment_id)
-            .collect()
-    }
-    
-    #[cfg(test)]
     pub fn segment_entry(&self, segment_id: &SegmentId) -> Option {
         self.segment_states
             .get(&segment_id)
             .map(|segment_entry| segment_entry.clone())
     }
-
-    pub fn contains(&self, segment_id: SegmentId) -> bool {
-        self.segment_states.contains_key(&segment_id)
-    }
-
-
+    
     pub fn contains_all(&mut self, segment_ids: &[SegmentId]) -> bool {
         segment_ids
             .iter()
@@ -116,21 +86,21 @@ impl SegmentRegister {
     }
     
     pub fn add_segment_entry(&mut self, segment_entry: SegmentEntry) {
-        let segment_id = segment_entry.meta.segment_id;
+        let segment_id = segment_entry.segment_id();
         self.segment_states.insert(segment_id, segment_entry);
     }
     
-    pub fn add_segment(&mut self, segment_meta: SegmentMeta) {
-        self.add_segment_entry(SegmentEntry {
-            meta: segment_meta.clone(),
-            state: SegmentState::Ready,
-        });
-    }
-    
     pub fn remove_segment(&mut self, segment_id: &SegmentId) {
         self.segment_states.remove(segment_id);
     }   
     
+    pub fn cancel_merge(&mut self, segment_id: &SegmentId) {
+        self.segment_states
+            .get_mut(segment_id)
+            .expect("Received a merge notification for a segment that is not registered")
+            .cancel_merge();
+    }
+
     pub fn start_merge(&mut self, segment_id: &SegmentId) {
         self.segment_states
             .get_mut(segment_id)
@@ -138,63 +108,73 @@ impl SegmentRegister {
             .start_merge();
     } 
     
-    
-}
-
-
-impl From> for SegmentRegister {
-    fn from(segment_metas: Vec) -> SegmentRegister {
+    pub fn new(segment_metas: Vec, delete_cursor: DeleteCursor) -> SegmentRegister {
         let mut segment_states = HashMap::new();
         for segment_meta in segment_metas {
-            let segment_id = segment_meta.segment_id;
-            let segment_entry = SegmentEntry {
-                meta: segment_meta,
-                state: SegmentState::Ready,
-                
-            };
+            let segment_id = segment_meta.id();
+            let segment_entry = SegmentEntry::new(
+                segment_meta,
+                delete_cursor.clone(),
+                None);
             segment_states.insert(segment_id, segment_entry);
         }
         SegmentRegister {
-            segment_states: segment_states,
+            segment_states: segment_states
         }
     }
 }
 
-impl Default for SegmentRegister {
-    fn default() -> SegmentRegister {
-        SegmentRegister {
-            segment_states: HashMap::new(),
-        }
-    }
-}
 
 #[cfg(test)]
 mod tests {
-    
+    use indexer::SegmentState;
     use core::SegmentId;
     use core::SegmentMeta;
+    use indexer::delete_queue::*;
     use super::*;
+
+    fn segment_ids(segment_register: &SegmentRegister) -> Vec {
+        segment_register
+            .segment_metas()
+            .into_iter()
+            .map(|segment_meta| segment_meta.id())
+            .collect()
+    }
     
     #[test]
     fn test_segment_register() {
+        let delete_queue = DeleteQueue::new();
+
         let mut segment_register = SegmentRegister::default();
         let segment_id_a = SegmentId::generate_random();
         let segment_id_b = SegmentId::generate_random();
         let segment_id_merged = SegmentId::generate_random();
-        let segment_meta_merged = SegmentMeta::new(segment_id_merged, 10 + 20);
-        segment_register.add_segment(SegmentMeta::new(segment_id_a, 10));
-        assert_eq!(segment_register.segment_entry(&segment_id_a).unwrap().state, SegmentState::Ready);
-        assert_eq!(segment_register.segment_ids(), vec!(segment_id_a));
-        segment_register.add_segment(SegmentMeta::new(segment_id_b, 20));
-        assert_eq!(segment_register.segment_entry(&segment_id_b).unwrap().state, SegmentState::Ready);
+        
+        {
+            let segment_meta = SegmentMeta::new(segment_id_a);
+            let segment_entry = SegmentEntry::new(segment_meta,  delete_queue.cursor(), None);
+            segment_register.add_segment_entry(segment_entry);
+        }
+        assert_eq!(segment_register.segment_entry(&segment_id_a).unwrap().state(), SegmentState::Ready);
+        assert_eq!(segment_ids(&segment_register), vec!(segment_id_a));
+        {
+            let segment_meta = SegmentMeta::new(segment_id_b);
+            let segment_entry = SegmentEntry::new(segment_meta,  delete_queue.cursor(), None);
+            segment_register.add_segment_entry(segment_entry);
+        }
+        assert_eq!(segment_register.segment_entry(&segment_id_b).unwrap().state(), SegmentState::Ready);
         segment_register.start_merge(&segment_id_a);
         segment_register.start_merge(&segment_id_b);
-        assert_eq!(segment_register.segment_entry(&segment_id_a).unwrap().state, SegmentState::InMerge);
-        assert_eq!(segment_register.segment_entry(&segment_id_b).unwrap().state, SegmentState::InMerge);
+        assert_eq!(segment_register.segment_entry(&segment_id_a).unwrap().state(), SegmentState::InMerge);
+        assert_eq!(segment_register.segment_entry(&segment_id_b).unwrap().state(), SegmentState::InMerge);
         segment_register.remove_segment(&segment_id_a);
         segment_register.remove_segment(&segment_id_b);
-        segment_register.add_segment(segment_meta_merged);        
-        assert_eq!(segment_register.segment_ids(), vec!(segment_id_merged));        
+        {
+            let segment_meta_merged = SegmentMeta::new(segment_id_merged);
+            let segment_entry = SegmentEntry::new(segment_meta_merged,  delete_queue.cursor(), None);
+            segment_register.add_segment_entry(segment_entry);        
+        }
+        assert_eq!(segment_ids(&segment_register), vec!(segment_id_merged));        
     }
     
 }
\ No newline at end of file
diff --git a/src/indexer/segment_serializer.rs b/src/indexer/segment_serializer.rs
index bfbca0faf..e84a24c33 100644
--- a/src/indexer/segment_serializer.rs
+++ b/src/indexer/segment_serializer.rs
@@ -1,9 +1,6 @@
 use Result;
 
-use std::io::Write;
-use rustc_serialize::json;
 use core::Segment;
-use core::SegmentInfo;
 use core::SegmentComponent;
 use fastfield::FastFieldSerializer;
 use store::StoreWriter;
@@ -13,7 +10,6 @@ use postings::PostingsSerializer;
 /// Segment serializer is in charge of laying out on disk
 /// the data accumulated and sorted by the `SegmentWriter`.
 pub struct SegmentSerializer {
-    segment: Segment,
     store_writer: StoreWriter,
     fast_field_serializer: FastFieldSerializer,
     fieldnorms_serializer: FastFieldSerializer,
@@ -33,7 +29,6 @@ impl SegmentSerializer {
 
         let postings_serializer = try!(PostingsSerializer::open(segment));
         Ok(SegmentSerializer {
-            segment: segment.clone(),
             postings_serializer: postings_serializer,
             store_writer: StoreWriter::new(store_write),
             fast_field_serializer: fast_field_serializer,
@@ -61,16 +56,6 @@ impl SegmentSerializer {
         &mut self.store_writer
     }
 
-    /// Write the `SegmentInfo`
-    pub fn write_segment_info(&mut self, segment_info: &SegmentInfo) -> Result<()> {
-        let mut write = try!(self.segment.open_write(SegmentComponent::INFO));
-        let json_data = json::encode(segment_info)
-            .expect("Encoding to segment_info to JSON failed. This should never happen");
-        try!(write.write_all(json_data.as_bytes()));
-        try!(write.flush());
-        Ok(())
-    }
-
     /// Finalize the segment serialization.
     pub fn close(self) -> Result<()> {
         try!(self.fast_field_serializer.close());
diff --git a/src/indexer/segment_updater.rs b/src/indexer/segment_updater.rs
index 2a1b3e577..4ac7ddea7 100644
--- a/src/indexer/segment_updater.rs
+++ b/src/indexer/segment_updater.rs
@@ -1,44 +1,43 @@
 #![allow(for_kv_map)]
 
-use chan;
 use core::Index;
-use std::sync::Mutex;
+use core::IndexMeta;
+use core::META_FILEPATH;
 use core::Segment;
 use core::SegmentId;
 use core::SegmentMeta;
-use std::mem;
 use core::SerializableSegment;
-use indexer::MergePolicy;
+use directory::Directory;
+use indexer::stamper::Stamper;
+use Error;
+use futures_cpupool::CpuPool;
+use futures::Future;
+use futures::Canceled;
+use futures::oneshot;
+use directory::FileProtection;
+use indexer::{MergePolicy, DefaultMergePolicy};
+use indexer::index_writer::advance_deletes;
 use indexer::MergeCandidate;
 use indexer::merger::IndexMerger;
+use indexer::SegmentEntry;
 use indexer::SegmentSerializer;
-use std::thread;
-use schema::Schema;
-use directory::Directory;
-use std::thread::JoinHandle;
-use std::sync::Arc;
-use std::collections::HashMap;
-use rustc_serialize::json;
 use Result;
-use core::IndexMeta;
-use core::META_FILEPATH;
+use futures_cpupool::CpuFuture;
+use rustc_serialize::json;
+use indexer::delete_queue::DeleteCursor;
+use schema::Schema;
+use std::borrow::BorrowMut;
+use std::collections::HashMap;
 use std::io::Write;
-use super::segment_manager::{SegmentManager, get_segment_ready_for_commit};
-use super::super::core::index::get_segment_manager;
-
-pub type SegmentUpdateSender = chan::Sender;
-pub type SegmentUpdateReceiver = chan::Receiver;
-
-
-fn create_metas(segment_manager: &SegmentManager, schema: Schema, docstamp: u64) -> IndexMeta {
-    let (committed_segments, uncommitted_segments) = segment_manager.segment_metas();
-    IndexMeta {
-        committed_segments: committed_segments,
-        uncommitted_segments: uncommitted_segments,
-        schema: schema,
-        docstamp: docstamp,
-    }
-}
+use std::mem;
+use std::ops::DerefMut;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, AtomicBool};
+use std::sync::atomic::Ordering;
+use std::sync::RwLock;
+use std::thread;
+use std::thread::JoinHandle;
+use super::segment_manager::{SegmentManager, get_mergeable_segments};
 
 
 /// Save the index meta file.
@@ -51,11 +50,10 @@ fn create_metas(segment_manager: &SegmentManager, schema: Schema, docstamp: u64)
 ///
 /// This method is not part of tantivy's public API
 pub fn save_new_metas(schema: Schema,
-                  docstamp: u64,
+                  opstamp: u64,
                   directory: &mut Directory)
                   -> Result<()> {
-    let segment_manager = SegmentManager::from_segments(Vec::new());
-    save_metas(&segment_manager, schema, docstamp, directory)
+    save_metas(vec!(), schema, opstamp, directory)
 }
 
 
@@ -69,305 +67,429 @@ pub fn save_new_metas(schema: Schema,
 /// and flushed.
 ///
 /// This method is not part of tantivy's public API
-pub fn save_metas(segment_manager: &SegmentManager,
+pub fn save_metas(segment_metas: Vec,
                   schema: Schema,
-                  docstamp: u64,
+                  opstamp: u64,
                   directory: &mut Directory)
                   -> Result<()> {
-    let metas = create_metas(segment_manager, schema, docstamp);
-    let mut w = Vec::new();
+    let metas = IndexMeta {
+        segments: segment_metas,
+        schema: schema,
+        opstamp: opstamp,
+    };
+    let mut w = vec!();
     try!(write!(&mut w, "{}\n", json::as_pretty_json(&metas)));
-    directory.atomic_write(&META_FILEPATH, &w[..])
-        .map_err(From::from)
+    let res = directory.atomic_write(&META_FILEPATH, &w[..])?;
+    debug!("Saved metas {}", json::as_pretty_json(&metas));
+    Ok(res)
+        
 }
 
 
-#[derive(Debug, Clone)]
-pub enum SegmentUpdate {
+// The segment update runner is in charge of processing all
+//  of the `SegmentUpdate`s.
+//
+// All this processing happens on a single thread
+// consuming a common queue. 
+#[derive(Clone)]
+pub struct SegmentUpdater(Arc);
+
+
+
+fn perform_merge(segment_ids: &[SegmentId],
+                 segment_updater: &SegmentUpdater,
+                 mut merged_segment: Segment,
+                 target_opstamp: u64) -> Result {
+    // first we need to apply deletes to our segment.
+    info!("Start merge: {:?}", segment_ids);
     
-    /// New segment added.
-    /// Created by the indexing worker thread 
-    AddSegment(SegmentMeta),
+    let ref index = segment_updater.0.index;
+    let schema = index.schema();
+    let mut segment_entries = vec!();
+
+    let mut file_protections: Vec = vec!();
+
+    for segment_id in segment_ids {
+        if let Some(mut segment_entry) = segment_updater.0
+            .segment_manager
+            .segment_entry(segment_id) {
+            let segment = index.segment(segment_entry.meta().clone());
+            if let Some(file_protection) = advance_deletes(segment, &mut segment_entry, target_opstamp)? {
+                file_protections.push(file_protection);
+            }
+            segment_entries.push(segment_entry);
+        }
+        else {
+            error!("Error, had to abort merge as some of the segment is not managed anymore.a");
+            return Err(Error::InvalidArgument(format!("Segment {:?} requested for merge is not managed.", segment_id)));
+        }
+    }
     
-    /// A merge is ended.
-    /// Remove the merged segment and record the new 
-    /// large merged segment.
-    EndMerge(usize, Vec, SegmentMeta),
+    let delete_cursor = segment_entries[0].delete_cursor().clone();
+
+    let segments: Vec = segment_entries
+        .iter()
+        .map(|segment_entry| {
+            index.segment(segment_entry.meta().clone())
+        })
+        .collect();
+        
     
-    /// Happens when rollback is called.
-    /// The current generation of segments is cancelled.
-    CancelGeneration,
+    // An IndexMerger is like a "view" of our merged segments.
+    let merger: IndexMerger = IndexMerger::open(schema, &segments[..])?;
+
+    // ... we just serialize this index merger in our new segment
+    // to merge the two segments.
+
+    let segment_serializer =
+        SegmentSerializer::for_segment(&mut merged_segment)
+        .expect("Creating index serializer failed");
+
+    let num_docs = merger.write(segment_serializer).expect("Serializing merged index failed");
+    let mut segment_meta = SegmentMeta::new(merged_segment.id());
+    segment_meta.set_max_doc(num_docs);
     
-    /// Starts a new generation... This 
-    /// happens at the end of Rollback.
-    NewGeneration,
-    
-    /// Just dropping the Segment updater object
-    /// is safe, but some merge might be happening in 
-    /// the background and the user may want to wait for these 
-    /// threads to terminate.
-    /// 
-    /// When receiving the Terminate signal, the segment updater stops
-    /// receiving segment updates and just waits for the merging threads
-    /// to terminate.
-	Terminate,
-    
-    /// Commit marks uncommmitted segments as committed.
-	Commit(u64),
+    let after_merge_segment_entry = SegmentEntry::new(segment_meta.clone(), delete_cursor, None);
+    Ok(after_merge_segment_entry)
 }
 
 
-
-
-
-/// The segment updater is in charge of processing all of the 
-/// `SegmentUpdate`s.
-///
-/// All this processing happens on a single thread
-/// consuming a common queue. 
-/// 
-/// The segment updates producers are :
-/// - indexing threads are sending new segments 
-/// - merging threads are sending merge operations
-/// - the index writer sends "terminate"
-pub struct SegmentUpdater {
-	index: Index,
-	is_cancelled_generation: bool,
-	segment_update_receiver: SegmentUpdateReceiver,
-	segment_update_sender: SegmentUpdateSender,
-    segment_manager_arc: Arc,
-    merge_policy: Arc>>,
-    merging_thread_id: usize,
-    merging_threads: HashMap, SegmentMeta)> >, 
+struct InnerSegmentUpdater {
+    pool: CpuPool,
+    index: Index,
+    segment_manager: SegmentManager,
+    merge_policy: RwLock>,
+    merging_thread_id: AtomicUsize,
+    merging_threads: RwLock>>>,
+    generation: AtomicUsize,
+    killed: AtomicBool, 
+    stamper: Stamper,
 }
 
-
 impl SegmentUpdater {
-	    
-    pub fn start_updater(index: Index, merge_policy: Arc>>) -> (SegmentUpdateSender, JoinHandle<()>) {
-        let segment_updater = SegmentUpdater::new(index, merge_policy);
-        (segment_updater.segment_update_sender.clone(), segment_updater.start())
+
+    pub fn new(index: Index,
+               stamper: Stamper,
+               delete_cursor: DeleteCursor) -> Result {
+        let segments = index.searchable_segment_metas()?;
+        let segment_manager = SegmentManager::from_segments(segments, delete_cursor);
+        Ok(
+            SegmentUpdater(Arc::new(InnerSegmentUpdater {
+                pool: CpuPool::new(1),
+                index: index,
+                segment_manager: segment_manager,
+                merge_policy: RwLock::new(box DefaultMergePolicy::default()),
+                merging_thread_id: AtomicUsize::default(),
+                merging_threads: RwLock::new(HashMap::new()),
+                generation: AtomicUsize::default(),
+                killed: AtomicBool::new(false),
+                stamper: stamper,
+            }))
+        )
     }
-    
-    fn new(index: Index, merge_policy: Arc>>) -> SegmentUpdater {
-        let segment_manager_arc = get_segment_manager(&index);
-        let (segment_update_sender, segment_update_receiver): (SegmentUpdateSender, SegmentUpdateReceiver) = chan::async();
-		SegmentUpdater {
-			index: index,
-            is_cancelled_generation: false,
-            segment_update_sender: segment_update_sender,
-            segment_update_receiver: segment_update_receiver,
-            segment_manager_arc: segment_manager_arc,
-            merge_policy: merge_policy,
-            merging_thread_id: 0,
-            merging_threads: HashMap::new(), 
-		}
-	}
-    
-    fn new_merging_thread_id(&mut self,) -> usize {
-        self.merging_thread_id += 1;
-        self.merging_thread_id
+
+    pub fn new_segment(&self) -> Segment {
+        let new_segment = self.0.index.new_segment();
+        let segment_id = new_segment.id();
+        self.0.segment_manager.write_segment(segment_id);
+        new_segment
     }
-    
-    
-    fn end_merge(
-        &mut self,
-        segment_ids: Vec,
-        segment_meta: SegmentMeta) {
-        
-        let segment_manager = self.segment_manager_arc.clone();
-        segment_manager.end_merge(&segment_ids, &segment_meta);
-        save_metas(
-            &*segment_manager,
-            self.index.schema(),
-            self.index.docstamp(),
-            self.index.directory_mut()).expect("Could not save metas.");
-        for segment_id in segment_ids {
-            self.index.delete_segment(segment_id);
+
+    pub fn get_merge_policy(&self) -> Box {
+        self.0.merge_policy.read().unwrap().box_clone()
+    }
+
+    pub fn set_merge_policy(&self, merge_policy: Box) {
+        *self.0.merge_policy.write().unwrap()= merge_policy;
+    }
+
+    fn get_merging_thread_id(&self) -> usize {
+        self.0.merging_thread_id.fetch_add(1, Ordering::SeqCst)
+    }
+
+    fn run_async T>(&self, f: F) -> CpuFuture {
+        let me_clone = self.clone();
+        self.0.pool.spawn_fn(move || {
+            Ok(f(me_clone))
+        })
+    }
+
+
+    pub fn add_segment(&self, generation: usize, segment_entry: SegmentEntry) -> bool {
+        if generation >= self.0.generation.load(Ordering::Acquire) {
+            self.run_async(|segment_updater| {
+                segment_updater.0.segment_manager.add_segment(segment_entry);
+                segment_updater.consider_merge_options();
+                true
+            }).forget();
+            true
+        }
+        else {
+            false
         }
     }
 
+    pub fn kill(&mut self,) {
+        self.0.killed.store(true, Ordering::Release);
+    }
 
-    fn start_merges(&mut self,) {
-        
-        let merge_candidates = self.consider_merge_options();
-        
-        for MergeCandidate(segment_ids) in merge_candidates {
-            
-            let merging_thread_id = self.new_merging_thread_id();
-            
-            self.segment_manager().start_merge(&segment_ids);
+    fn is_alive(&self,) -> bool {
+        !self.0.killed.load(Ordering::Acquire)
+    }
 
-            let index_clone = self.index.clone();
-            let segment_update_sender_clone = self.segment_update_sender.clone();
-            
-            let merge_thread_handle = thread::Builder::new()
-                .name(format!("merge_thread_{:?}", merging_thread_id))
-                .spawn(move || {
-                    info!("Start merge: {:?}", segment_ids);
-                    let schema = index_clone.schema();
-                    let segments: Vec = segment_ids
-                        .iter()
-                        .map(|&segment_id| index_clone.segment(segment_id))
-                        .collect();
-                    // An IndexMerger is like a "view" of our merged segments. 
-                    // TODO unwrap
-                    let merger: IndexMerger = IndexMerger::open(schema, &segments[..]).expect("Creating index merger failed");
-                    let mut merged_segment = index_clone.new_segment();
-                    // ... we just serialize this index merger in our new segment
-                    // to merge the two segments.
-                    let segment_serializer = SegmentSerializer::for_segment(&mut merged_segment).expect("Creating index serializer failed");
-                    let num_docs = merger.write(segment_serializer).expect("Serializing merged index failed");
-                    let segment_meta = SegmentMeta {
-                        segment_id: merged_segment.id(),
-                        num_docs: num_docs,
-                    };
-                    let segment_update = SegmentUpdate::EndMerge(merging_thread_id, segment_ids.clone(), segment_meta.clone());
-                    segment_update_sender_clone.send(segment_update.clone());
-                    (segment_ids, segment_meta)
-                })
-                .expect("Failed to spawn merge thread");
-            
-            self.merging_threads.insert(merging_thread_id, merge_thread_handle);
+
+    /// Apply deletes up to the target opstamp to all segments.
+    ///
+    /// Tne method returns copies of the segment entries,
+    /// updated with the delete information.
+    fn purge_deletes(&self, target_opstamp: u64) -> Result> {
+        let mut segment_entries = self.0.segment_manager.segment_entries(); 
+        for segment_entry in &mut segment_entries {
+            let segment = self.0.index.segment(segment_entry.meta().clone());
+            advance_deletes(segment, segment_entry, target_opstamp)?;
+        }
+        Ok(segment_entries)
+        
+    }
+
+    pub fn save_metas(&self, opstamp: u64) {
+        if self.is_alive() {
+            let index = &self.0.index;
+            let directory = index.directory();
+            save_metas(
+                self.0.segment_manager.committed_segment_metas(),
+                index.schema(),
+                opstamp,
+                directory.box_clone().borrow_mut()).expect("Could not save metas.");
         }
     }
-    
-    fn consider_merge_options(&self,) -> Vec {
-        let segment_manager = self.segment_manager();
-        let (committed_segments, uncommitted_segments) = get_segment_ready_for_commit(segment_manager);
-        // Committed segments cannot be merged with uncommitted_segments.
-        // We therefore consider merges using these two sets of segments independantly.
-        let merge_policy_lock = self.merge_policy.lock().unwrap();
-        let mut merge_candidates = merge_policy_lock.compute_merge_candidates(&uncommitted_segments);
-        let committed_merge_candidates = merge_policy_lock.compute_merge_candidates(&committed_segments);
-        merge_candidates.extend_from_slice(&committed_merge_candidates[..]);
-        merge_candidates
-    }
-    
-    
-	fn segment_manager(&self,) -> &SegmentManager {
-		&*self.segment_manager_arc
-	}
-    
-    pub fn start(self,) -> JoinHandle<()> {
-		thread::Builder::new()
-            .name("segment_update".to_string())
-            .spawn(move || {
-                self.process();
-		    })
-            .expect("Failed to start segment updater thread.")
-    }
-    
-	fn process(mut self,) {
-        
-        let segment_manager = self.segment_manager_arc.clone();
-        
-        for segment_update in self.segment_update_receiver.clone() {
-            
-            if let SegmentUpdate::Terminate = segment_update {
-                break;
+
+    pub fn commit(&self, opstamp: u64) -> Result<()> {
+        self.run_async(move |segment_updater| {
+            let mut index = segment_updater.0.index.clone();
+
+            if segment_updater.is_alive() {
+                let segment_entries = segment_updater
+                    .purge_deletes(opstamp)
+                    .expect("Failed purge deletes");
+                segment_updater.0.segment_manager.commit(segment_entries);
+                segment_updater.save_metas(opstamp);
+                let living_files = segment_updater.0.segment_manager.list_files();
+                index.directory_mut().garbage_collect(living_files);
+                segment_updater.consider_merge_options();
             }
-                
-            // we check the generation number as if it was 
-            // dirty-bit. If the value is different 
-            // to our generation, then the segment_manager has
-            // been update updated.
-            let generation_before_update = segment_manager.generation();
-            
-            self.process_one(segment_update);
-            
-            if generation_before_update != segment_manager.generation() {
-                // The segment manager has changed, we need to   
-                // - save meta.json	
-                save_metas(
-                    &*segment_manager,
-                    self.index.schema(),
-                    self.index.docstamp(),
-                    self.index.directory_mut()).expect("Could not save metas.");
+        }).wait()
+    }
 
 
-                // - update the searchers
-                
-                // update the searchers so that they eventually will
-                // use the new segments.
-                // TODO eventually have this work through watching meta.json
-                // so that an external process stays up to date as well. 
-                match self.index.load_searchers() {
-                    Ok(()) => {
-                    }
-                    Err(e) => {
-                        error!("Failure while loading new searchers {:?}", e);
-                        panic!(format!("Failure while loading new searchers {:?}", e));
-                    }
-                }
-                
-                // - start merges if required
-                self.start_merges();
-            }
+    pub fn start_merge(&self, segment_ids: &[SegmentId]) -> impl Future {
+        
+        self.0.segment_manager.start_merge(segment_ids);
+        let segment_updater_clone = self.clone();
+        
+        let segment_ids_vec = segment_ids.to_vec(); 
+        
+        let merging_thread_id = self.get_merging_thread_id();
+        let (merging_future_send, merging_future_recv) = oneshot();
+        
+        if segment_ids.is_empty() {
+            return merging_future_recv;
         }
         
-        let mut merging_threads = HashMap::new();
-        mem::swap(&mut merging_threads, &mut self.merging_threads);
-        for (_, merging_thread_handle) in merging_threads {
-            match merging_thread_handle.join() {
-                Ok((segment_ids, segment_meta)) => {
-                    self.end_merge(segment_ids, segment_meta);
+        let target_opstamp = self.0.stamper.stamp();
+        let merging_join_handle = thread::spawn(move || {
+            
+            // first we need to apply deletes to our segment.
+            info!("Start merge: {:?}", segment_ids_vec);
+            
+            let merged_segment = segment_updater_clone.new_segment(); 
+            let merged_segment_id = merged_segment.id();
+            let merge_result = perform_merge(&segment_ids_vec, &segment_updater_clone, merged_segment, target_opstamp);
+
+            match merge_result {
+                Ok(after_merge_segment_entry) => {
+                    let merged_segment_meta = after_merge_segment_entry.meta().clone();
+                    segment_updater_clone
+                        .end_merge(segment_ids_vec, after_merge_segment_entry)
+                        .expect("Segment updater thread is corrupted.");
+                    
+                    // the future may fail if the listener of the oneshot future 
+                    // has been destroyed.
+                    //
+                    // This is not a problem here, so we just ignore any 
+                    // possible error.
+                    let _merging_future_res = merging_future_send.send(merged_segment_meta);
                 }
                 Err(e) => {
-                    error!("Error in merging thread {:?}", e);
-                    break;
-                } 
+                    error!("Merge of {:?} was cancelled: {:?}", segment_ids_vec, e);
+                    // ... cancel merge
+                    if cfg!(test) {
+                        panic!("Merge failed.");
+                    }
+                    segment_updater_clone.cancel_merge(&segment_ids_vec, merged_segment_id);
+                    // merging_future_send will be dropped, sending an error to the future.
+                }
             }
+            segment_updater_clone.0.merging_threads.write().unwrap().remove(&merging_thread_id);
+            Ok(())
+        });
+        self.0.merging_threads.write().unwrap().insert(merging_thread_id, merging_join_handle);
+        merging_future_recv
+    }
+
+
+    fn consider_merge_options(&self) {
+        let (committed_segments, uncommitted_segments) = get_mergeable_segments(&self.0.segment_manager);
+        // Committed segments cannot be merged with uncommitted_segments.
+        // We therefore consider merges using these two sets of segments independently.
+        let merge_policy = self.get_merge_policy();
+        let mut merge_candidates = merge_policy.compute_merge_candidates(&uncommitted_segments);
+        let committed_merge_candidates = merge_policy.compute_merge_candidates(&committed_segments);
+        merge_candidates.extend_from_slice(&committed_merge_candidates[..]);
+        for MergeCandidate(segment_metas) in merge_candidates {
+            self.start_merge(&segment_metas);
         }
     }
 
-    
+    fn cancel_merge(&self, 
+        before_merge_segment_ids: &[SegmentId],
+        after_merge_segment_entry: SegmentId)  {
+        self.0.segment_manager.cancel_merge(&before_merge_segment_ids, after_merge_segment_entry);
+    }
 
     
-	// Process a single segment update.
-	pub fn process_one(
-		&mut self,
-		segment_update: SegmentUpdate) {
-		
-		info!("Segment update: {:?}", segment_update);
+    fn end_merge(&self, 
+        before_merge_segment_ids: Vec,
+        mut after_merge_segment_entry: SegmentEntry) -> Result<()> {
         
-		match segment_update {
-			SegmentUpdate::AddSegment(segment_meta) => {
-				if !self.is_cancelled_generation {
-					self.segment_manager().add_segment(segment_meta);
-				}
-				else {
-					// rollback has been called and this
-					// segment actually belong to the 
-					// documents that have been dropped.
-					//
-					// Let's just remove its files.
-					self.index.delete_segment(segment_meta.segment_id);
-				}
-			}
-			SegmentUpdate::EndMerge(merging_thread_id, segment_ids, segment_meta) => {
-                self.end_merge(
-                    segment_ids,
-                    segment_meta);
-                self.merging_threads.remove(&merging_thread_id);
-			}
-			SegmentUpdate::CancelGeneration => {
-				// Called during rollback. The segment 
-				// that will arrive will be ignored
-				// until a NewGeneration is update arrives.
-				self.is_cancelled_generation = true;
-			}
-			SegmentUpdate::NewGeneration => {
-				// After rollback, we can resume
-				// indexing new documents.
-				self.is_cancelled_generation = false;
-			}
-			SegmentUpdate::Commit(docstamp) => {
-				self.segment_manager().commit(docstamp);
-			}
-			SegmentUpdate::Terminate => {
-                panic!("We should have left the loop before processing it.");
-			}
-		}
-	}
+        self.run_async(move |segment_updater| {
+            debug!("End merge {:?}", after_merge_segment_entry.meta());
+            let mut delete_cursor = after_merge_segment_entry.delete_cursor().clone();
+            if let Some(delete_operation) = delete_cursor.get() {
+                let committed_opstamp = segment_updater.0.index.opstamp();
+                if delete_operation.opstamp < committed_opstamp {
+                    let segment = segment_updater.0.index.segment(after_merge_segment_entry.meta().clone());
+                    // TODO check unwrap
+                    advance_deletes(segment, &mut after_merge_segment_entry, committed_opstamp).unwrap();
+                }
+            }
+            segment_updater.0.segment_manager.end_merge(&before_merge_segment_ids, after_merge_segment_entry);
+            segment_updater.consider_merge_options();
+            segment_updater.save_metas(segment_updater.0.index.opstamp());
+        }).wait()
+    }
+
+
+    /// Wait for current merging threads.
+    ///
+    /// Upon termination of the current merging threads,
+    /// merge opportunity may appear.
+    // 
+    /// We keep waiting until the merge policy judges that
+    /// no opportunity is available.
+    ///
+    /// Note that it is not required to call this 
+    /// method in your application.
+    /// Terminating your application without letting 
+    /// merge terminate is perfectly safe.
+    /// 
+    /// Obsolete files will eventually be cleaned up
+    /// by the directory garbage collector.
+    pub fn wait_merging_thread(&self) -> Result<()> {
+
+        let mut num_segments: usize;
+        loop {
+            
+            num_segments = self.0.segment_manager.num_segments();
+
+            let mut new_merging_threads = HashMap::new();
+            {
+                let mut merging_threads = self.0.merging_threads.write().unwrap();
+                mem::swap(&mut new_merging_threads, merging_threads.deref_mut());
+            }
+            debug!("wait merging thread {}", new_merging_threads.len());
+            for (_, merging_thread_handle) in new_merging_threads {
+                merging_thread_handle
+                    .join()
+                    .map(|_| ())
+                    .map_err(|_| {
+                        Error::ErrorInThread("Merging thread failed.".to_string())
+                    })?
+            }
+            // Our merging thread may have queued their completed
+            self.run_async(move |_| {}).wait()?;
+
+            let new_num_segments = self.0.segment_manager.num_segments();
+
+            if new_num_segments >= num_segments {
+                break;
+            }
+        }      
+        Ok(())
+    }
+
+}
+
+
+
+
+#[cfg(test)]
+mod tests {
+
+    use Index;
+    use schema::*;
+    use indexer::merge_policy::tests::MergeWheneverPossible;
+
+    #[test]
+    fn test_delete_during_merge() {
+        let mut schema_builder = SchemaBuilder::default();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+
+        let index = Index::create_in_ram(schema);
+        
+        // writing the segment
+        let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+        index_writer.set_merge_policy(box MergeWheneverPossible);
+
+        {
+            for _ in 0..100 {
+                index_writer.add_document(doc!(text_field=>"a"));
+                index_writer.add_document(doc!(text_field=>"b"));
+            }
+            assert!(index_writer.commit().is_ok());
+        }
+        
+        {
+            for _ in 0..100 {
+                index_writer.add_document(doc!(text_field=>"c"));
+                index_writer.add_document(doc!(text_field=>"d"));
+            }
+            assert!(index_writer.commit().is_ok());
+        }
+        
+        {
+            index_writer.add_document(doc!(text_field=>"e"));
+            index_writer.add_document(doc!(text_field=>"f"));
+            assert!(index_writer.commit().is_ok());
+        }
+
+        {
+            let term = Term::from_field_text(text_field, "a");
+            index_writer.delete_term(term);
+            assert!(index_writer.commit().is_ok());
+        }
+
+        index.load_searchers().unwrap();
+        assert_eq!(index.searcher().num_docs(), 302);
+
+        {
+            index_writer.wait_merging_threads()
+                        .expect(    "waiting for merging threads");
+        }
+
+        index.load_searchers().unwrap();
+        assert_eq!(index.searcher().segment_readers().len(), 1);
+        assert_eq!(index.searcher().num_docs(), 302);
+    }
 }
diff --git a/src/indexer/segment_writer.rs b/src/indexer/segment_writer.rs
index 17ddf91c4..63842f9f1 100644
--- a/src/indexer/segment_writer.rs
+++ b/src/indexer/segment_writer.rs
@@ -1,10 +1,8 @@
 use Result;
 use DocId;
 use std::io;
-use schema::Schema;
-use schema::Document;
+use schema::Schema;	
 use schema::Term;
-use core::SegmentInfo;
 use core::Segment;
 use core::SerializableSegment;
 use postings::PostingsWriter;
@@ -19,6 +17,8 @@ use postings::{NothingRecorder, TermFrequencyRecorder, TFAndPositionRecorder};
 use indexer::segment_serializer::SegmentSerializer;
 use datastruct::stacker::Heap;
 use indexer::index_writer::MARGIN_IN_BYTES;
+use super::operation::AddOperation;
+
 
 /// A `SegmentWriter` is in charge of creating segment index from a
 /// documents.
@@ -32,6 +32,7 @@ pub struct SegmentWriter<'a> {
 	segment_serializer: SegmentSerializer,
 	fast_field_writers: U32FastFieldsWriter,
 	fieldnorms_writer: U32FastFieldsWriter,
+	doc_opstamps: Vec,
 }
 
 
@@ -70,7 +71,6 @@ fn posting_from_field_entry<'a>(field_entry: &FieldEntry, heap: &'a Heap) -> Box
 
 impl<'a> SegmentWriter<'a> {
 	
-	
 	/// Creates a new `SegmentWriter`
 	///
 	/// The arguments are defined as follows
@@ -80,7 +80,9 @@ impl<'a> SegmentWriter<'a> {
 	/// the flushing behavior as a buffer limit
 	/// - segment: The segment being written  
 	/// - schema
-	pub fn for_segment(heap: &'a Heap, mut segment: Segment, schema: &Schema) -> Result> {
+	pub fn for_segment(heap: &'a Heap,
+					   mut segment: Segment,
+					   schema: &Schema) -> Result> {
 		let segment_serializer = try!(SegmentSerializer::for_segment(&mut segment));
 		let mut per_field_postings_writers: Vec> = Vec::new();
 		for field_entry in schema.fields() {
@@ -94,6 +96,7 @@ impl<'a> SegmentWriter<'a> {
 			fieldnorms_writer: create_fieldnorms_writer(schema),
 			segment_serializer: segment_serializer,
 			fast_field_writers: U32FastFieldsWriter::from_schema(schema),
+			doc_opstamps: Vec::with_capacity(1_000),
 		})
 	}
 	
@@ -101,18 +104,16 @@ impl<'a> SegmentWriter<'a> {
 	/// 
 	/// Finalize consumes the `SegmentWriter`, so that it cannot 
 	/// be used afterwards.
-	pub fn finalize(mut self,) -> Result<()> {
-		let segment_info = self.segment_info();
+	pub fn finalize(mut self) -> Result> {
 		for per_field_postings_writer in &mut self.per_field_postings_writers {
 			per_field_postings_writer.close(self.heap);
 		}
-		try!(write(&self.per_field_postings_writers,
+		write(&self.per_field_postings_writers,
 			  &self.fast_field_writers,
 			  &self.fieldnorms_writer,
-			  segment_info,
 			  self.segment_serializer,
-			  self.heap));
-		Ok(())
+			  self.heap)?;
+		Ok(self.doc_opstamps)
 	}
 	
 	/// Returns true iff the segment writer's buffer has reached capacity.
@@ -129,8 +130,10 @@ impl<'a> SegmentWriter<'a> {
 	/// Indexes a new document
 	///
 	/// As a user, you should rather use `IndexWriter`'s add_document.
-    pub fn add_document(&mut self, doc: &Document, schema: &Schema) -> io::Result<()> {
+    pub fn add_document(&mut self, add_operation: &AddOperation, schema: &Schema) -> io::Result<()> {
         let doc_id = self.max_doc;
+		let doc = &add_operation.document;
+		self.doc_opstamps.push(add_operation.opstamp);
         for (field, field_values) in doc.get_sorted_field_values() {
 			let field_posting_writer: &mut Box = &mut self.per_field_postings_writers[field.0 as usize];
 			let field_options = schema.get_field_entry(field);
@@ -165,7 +168,7 @@ impl<'a> SegmentWriter<'a> {
 			}
 		}
 		self.fieldnorms_writer.fill_val_up_to(doc_id);
-		self.fast_field_writers.add_document(doc);
+		self.fast_field_writers.add_document(&doc);
 		let stored_fieldvalues: Vec<&FieldValue> = doc
 			.field_values()
 			.iter()
@@ -177,14 +180,6 @@ impl<'a> SegmentWriter<'a> {
 		Ok(())
     }
 	
-	/// Creates the `SegmentInfo` that will be serialized along
-	/// with the index in JSON format.  
- 	fn segment_info(&self,) -> SegmentInfo {
-		SegmentInfo {
-			max_doc: self.max_doc
-		}
-	}
-	
 	
 	/// Max doc is 
 	/// - the number of documents in the segment assuming there is no deletes
@@ -212,26 +207,25 @@ impl<'a> SegmentWriter<'a> {
 fn write<'a>(per_field_postings_writers: &[Box],
 		 fast_field_writers: &U32FastFieldsWriter,
 		 fieldnorms_writer: &U32FastFieldsWriter,
-		 segment_info: SegmentInfo,
 	  	 mut serializer: SegmentSerializer,
-		 heap: &'a Heap,) -> Result {
-		for per_field_postings_writer in per_field_postings_writers.iter() {
+		 heap: &'a Heap,) -> Result<()> {
+		for per_field_postings_writer in per_field_postings_writers {
 			try!(per_field_postings_writer.serialize(serializer.get_postings_serializer(), heap));
 		}
 		try!(fast_field_writers.serialize(serializer.get_fast_field_serializer()));
 		try!(fieldnorms_writer.serialize(serializer.get_fieldnorms_serializer()));
-		try!(serializer.write_segment_info(&segment_info));
 		try!(serializer.close());
-		Ok(segment_info.max_doc)
+		Ok(())
 }
 
 impl<'a> SerializableSegment for SegmentWriter<'a> {
 	fn write(&self, serializer: SegmentSerializer) -> Result {
+		let max_doc = self.max_doc;
 		write(&self.per_field_postings_writers,
 		      &self.fast_field_writers,
 			  &self.fieldnorms_writer,
-			  self.segment_info(),
 		      serializer,
-			  self.heap)
+			  self.heap)?;
+		Ok(max_doc)
 	}
 }
diff --git a/src/indexer/stamper.rs b/src/indexer/stamper.rs
new file mode 100644
index 000000000..816eb6dc4
--- /dev/null
+++ b/src/indexer/stamper.rs
@@ -0,0 +1,17 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Arc;
+
+
+#[derive(Clone, Default)]
+pub struct Stamper(Arc);
+
+impl Stamper {
+
+    pub fn new(first_opstamp: u64) -> Stamper {
+        Stamper(Arc::new(AtomicU64::new(first_opstamp)))
+    }
+
+    pub fn stamp(&self,) -> u64 {
+        self.0.fetch_add(1u64, Ordering::SeqCst)
+    }
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index c7338b974..0b63aec19 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,10 +5,11 @@
 #![feature(box_syntax)]
 #![feature(optin_builtin_traits)]
 #![feature(conservative_impl_trait)]
+#![feature(integer_atomics)]
+
 #![cfg_attr(test, feature(test))]
 #![cfg_attr(test, feature(step_by))]
 #![doc(test(attr(allow(unused_variables), deny(warnings))))]
-#![feature(conservative_impl_trait)]
 
 // #![warn(missing_docs)]
 #![allow(unused_imports)]
@@ -46,14 +47,26 @@ extern crate combine;
 extern crate itertools;
 extern crate chan;
 extern crate crossbeam;
+extern crate bit_set;
+extern crate futures;
+extern crate futures_cpupool;
 
+#[cfg(test)]
+extern crate env_logger;
 
 #[cfg(feature="simdcompression")]
 extern crate libc;
 
+#[cfg(windows)]
+extern crate winapi;
+
 #[cfg(test)] extern crate test;
 #[cfg(test)] extern crate rand;
 
+
+#[cfg(test)]
+mod functional_test;
+
 #[macro_use]
 mod macros {
     macro_rules! get(
@@ -72,19 +85,22 @@ mod macros {
     );
 }
 
+pub use error::Error;
+
+/// Tantivy result.
+pub type Result = std::result::Result;
+
 mod core;
 mod compression;
 mod store;
 mod indexer;
 mod common;
 mod error;
-
-pub use error::{Result, Error};
-
 mod analyzer;
 pub mod datastruct;
 
 
+
 /// Query module
 pub mod query;
 /// Directory module
@@ -99,13 +115,9 @@ pub mod schema;
 pub mod fastfield;
 
 pub use directory::Directory;
-pub use core::searcher::Searcher;
-
-pub use core::Segment;
-pub use core::Index;
+pub use core::{Index, Segment, SegmentId, SegmentMeta, Searcher};
 pub use indexer::IndexWriter;
-pub use schema::Term;
-pub use schema::Document;
+pub use schema::{Term, Document};
 pub use core::SegmentReader;
 pub use self::common::TimerTree;
 
@@ -116,14 +128,16 @@ pub use postings::SegmentPostingsOption;
 
 pub use core::TermIterator;
 
-#[cfg(feature="simdcompression")]
-pub fn version() -> &'static str {
-    concat!(version!(), "-simd")  
-}
 
-#[cfg(not(feature="simdcompression"))]
+/// Expose the current version of tantivy, as well
+/// whether it was compiled with the simd compression.
 pub fn version() -> &'static str {
-    concat!(version!(), "-nosimd") 
+    if cfg!(feature="simdcompression") {
+        concat!(version!(), "-simd")  
+    }
+    else {
+        concat!(version!(), "-nosimd") 
+    }
 }
 
 /// Tantivy's makes it possible to personalize when 
@@ -183,8 +197,10 @@ mod tests {
     use Index;
     use core::SegmentReader;
     use query::BooleanQuery;
+    use postings::SegmentPostingsOption;
     use schema::*;
     use DocSet;
+    use IndexWriter;
     use Postings;
 
     #[test]
@@ -198,15 +214,15 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af b");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c d");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             assert!(index_writer.commit().is_ok());
         }
@@ -220,26 +236,27 @@ mod tests {
         let index = Index::create_in_ram(schema_builder.build());
         let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
         {
-            index_writer.add_document(doc!(text_field=>"a b c")).unwrap();
+            index_writer.add_document(doc!(text_field=>"a b c"));
             index_writer.commit().unwrap();
         }
         {
             {
                 let doc = doc!(text_field=>"a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().unwrap();
         }
         {
             let doc = doc!(text_field=>"c");
-            index_writer.add_document(doc).unwrap();
+            index_writer.add_document(doc);
             index_writer.commit().unwrap();
         }
         {
+            index.load_searchers().unwrap();
             let searcher = index.searcher();
             let term_a = Term::from_field_text(text_field, "a");
             assert_eq!(searcher.doc_freq(&term_a), 3);
@@ -262,20 +279,20 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!();
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().unwrap();
         }
         {
-            
+            index.load_searchers().unwrap();
             let searcher = index.searcher();
             let segment_reader: &SegmentReader = searcher.segment_reader(0);
             let fieldnorms_reader = segment_reader.get_fieldnorms_reader(text_field).unwrap();
@@ -285,6 +302,198 @@ mod tests {
         }
     }
 
+
+    #[test]
+    fn test_delete_postings1() {
+        let mut schema_builder = SchemaBuilder::default();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+        let index = Index::create_in_ram(schema);
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            {   // 0
+                let doc = doc!(text_field=>"a b");
+                index_writer.add_document(doc);
+            }
+            {   // 1
+                let doc = doc!(text_field=>" a c");
+                index_writer.add_document(doc);
+            }
+            {   // 2
+                let doc = doc!(text_field=>" b c");
+                index_writer.add_document(doc);
+            }
+            {   // 3
+                let doc = doc!(text_field=>" b d");
+                index_writer.add_document(doc);
+            }
+            {
+                index_writer.delete_term(Term::from_field_text(text_field, "c"));
+            }
+            {
+                index_writer.delete_term(Term::from_field_text(text_field, "a"));
+            }
+            {   // 4
+                let doc = doc!(text_field=>" b c");
+                index_writer.add_document(doc);
+            }
+            {   // 5
+                let doc = doc!(text_field=>" a");
+                index_writer.add_document(doc);
+            }
+            index_writer.commit().unwrap();
+        }
+        {
+            index.load_searchers().unwrap();
+            let searcher = index.searcher();
+            let reader = searcher.segment_reader(0);
+            assert!(reader.read_postings_all_info(&Term::from_field_text(text_field, "abcd")).is_none());
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "a")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 5);
+                assert!(!postings.advance());
+            }
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "b")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 3);
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 4);
+                assert!(!postings.advance());
+            }
+        }
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            {   // 0
+                let doc = doc!(text_field=>"a b");
+                index_writer.add_document(doc);
+            }
+            {   // 1
+                index_writer.delete_term(Term::from_field_text(text_field, "c"));
+            }
+            index_writer.rollback().unwrap();
+        }
+        {
+            index.load_searchers().unwrap();
+            let searcher = index.searcher();
+            let reader = searcher.segment_reader(0);
+            assert!(reader.read_postings_all_info(&Term::from_field_text(text_field, "abcd")).is_none());
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "a")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 5);
+                assert!(!postings.advance());
+            }
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "b")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 3);
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 4);
+                assert!(!postings.advance());
+            }
+        }
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            { 
+                let doc = doc!(text_field=>"a b");
+                index_writer.add_document(doc);
+            }
+            {   
+                index_writer.delete_term(Term::from_field_text(text_field, "c"));
+            }
+            index_writer = index_writer.rollback().unwrap();   
+            index_writer.delete_term(Term::from_field_text(text_field, "a"));
+            index_writer.commit().unwrap();
+        }
+        {
+            index.load_searchers().unwrap();
+            let searcher = index.searcher();
+            let reader = searcher.segment_reader(0);
+            assert!(reader.read_postings_all_info(&Term::from_field_text(text_field, "abcd")).is_none());
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "a")).unwrap();
+                assert!(!postings.advance());
+            }
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "b")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 3);
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 4);
+                assert!(!postings.advance());
+            }
+            {
+                let mut postings = reader.read_postings_all_info(&Term::from_field_text(text_field, "c")).unwrap();
+                assert!(postings.advance());
+                assert_eq!(postings.doc(), 4);
+                assert!(!postings.advance());
+            }
+        }
+    }
+
+
+    #[test]
+    fn test_indexed_u32() {
+        let mut schema_builder = SchemaBuilder::default();
+        let field = schema_builder.add_u32_field("text", U32_INDEXED);
+        let schema = schema_builder.build();
+        
+        let index = Index::create_in_ram(schema);
+        let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+        index_writer.add_document(
+            doc!(field=>1)
+        );
+        index_writer.commit().unwrap();
+        index.load_searchers().unwrap();
+        let searcher = index.searcher();
+        let term = Term::from_field_u32(field, 1u32);
+        let mut postings = searcher.segment_reader(0).read_postings(&term, SegmentPostingsOption::NoFreq).unwrap();
+        assert!(postings.advance());
+        assert_eq!(postings.doc(), 0);
+        assert!(!postings.advance());
+    }
+
+    #[test]
+    fn test_delete_postings2() {
+        let mut schema_builder = SchemaBuilder::default();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+        let index = Index::create_in_ram(schema);
+        
+        // writing the segment
+        let mut index_writer = index.writer_with_num_threads(2, 40_000_000).unwrap();
+        
+        let add_document = |index_writer: &mut IndexWriter, val: &'static str| {
+            let doc = doc!(text_field=>val);
+            index_writer.add_document(doc);
+        };
+        
+        let remove_document = |index_writer: &mut IndexWriter, val: &'static str| {
+            let delterm = Term::from_field_text(text_field, val);
+            index_writer.delete_term(delterm);
+        };
+
+        add_document(&mut index_writer, "63");
+        add_document(&mut index_writer, "70");
+        add_document(&mut index_writer, "34");
+        add_document(&mut index_writer, "1");
+        add_document(&mut index_writer, "38");
+        add_document(&mut index_writer, "33");
+        add_document(&mut index_writer, "40");
+        add_document(&mut index_writer, "17");
+        remove_document(&mut index_writer, "38");
+        remove_document(&mut index_writer, "34");
+        index_writer.commit().unwrap();
+        index.load_searchers().unwrap();
+        let searcher = index.searcher();
+        assert_eq!(searcher.num_docs(), 6);
+    }
+
     #[test]
     fn test_termfreq() {
         let mut schema_builder = SchemaBuilder::default();
@@ -296,11 +505,12 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af af af bc bc");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().unwrap();
         }
         {
+            index.load_searchers().unwrap();
             let searcher = index.searcher();
             let reader = searcher.segment_reader(0);
             assert!(reader.read_postings_all_info(&Term::from_field_text(text_field, "abcd")).is_none());
@@ -324,19 +534,20 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af af af b");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c d");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().unwrap();
         }
         {
+            index.load_searchers().unwrap();
             let searcher = index.searcher();
             let get_doc_ids = |terms: Vec| {
                 let query = BooleanQuery::new_multiterms_query(terms);
@@ -390,15 +601,15 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af b");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let doc = doc!(text_field=>"a b c d");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             index_writer.commit().unwrap();
         }
diff --git a/src/postings/chained_postings.rs b/src/postings/chained_postings.rs
deleted file mode 100644
index f07185918..000000000
--- a/src/postings/chained_postings.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-use DocId;
-use postings::Postings;
-use postings::OffsetPostings;
-use postings::DocSet;
-use postings::HasLen;
-
-/// Creates a posting object that chains two postings 
-/// together.
-///
-/// When iterating over the chained postings,
-/// it will consume all of the documents of the first postings, 
-/// and then iterate over the documents over the second postings.
-/// 
-/// The chained postings is used when merging segments. 
-pub struct ChainedPostings<'a> {
-    chained_postings: Vec>,
-    posting_id: usize,
-    len: usize,
-}
-
-impl<'a> From>> for ChainedPostings<'a> {
-    fn from(chained_postings: Vec>) -> ChainedPostings {
-        let len: usize = chained_postings
-            .iter()
-            .map(|segment_postings| segment_postings.len())
-            .sum();
-        ChainedPostings {
-            chained_postings: chained_postings,
-            posting_id: 0,
-            len: len,
-        }
-    }
-}
-
-impl<'a> DocSet for ChainedPostings<'a> {
-
-    fn advance(&mut self,) -> bool {
-        if self.posting_id == self.chained_postings.len() {
-            return false;
-        }
-        while !self.chained_postings[self.posting_id].advance() {
-            self.posting_id += 1;
-            if self.posting_id == self.chained_postings.len() {
-                return false;
-            }   
-        }
-        true
-    }
-
-    fn doc(&self,) -> DocId {
-        self.chained_postings[self.posting_id].doc()
-    }
-}
-
-impl<'a> HasLen for ChainedPostings<'a> {
-    fn len(&self,) -> usize {
-        self.len
-    }
-}
-
-impl<'a> Postings for ChainedPostings<'a> {
-    
-    fn term_freq(&self,) -> u32 {
-        self.chained_postings[self.posting_id].term_freq()
-    }
-    
-    fn positions(&self) -> &[u32] {
-        self.chained_postings[self.posting_id].positions()
-    } 
-    
-}
diff --git a/src/postings/docset.rs b/src/postings/docset.rs
index 9dda32559..e28319f42 100644
--- a/src/postings/docset.rs
+++ b/src/postings/docset.rs
@@ -67,6 +67,7 @@ pub trait DocSet {
     }
 }
 
+
 impl DocSet for Box {
     fn advance(&mut self) -> bool {
         let unboxed: &mut TDocSet = self.borrow_mut();
diff --git a/src/postings/intersection.rs b/src/postings/intersection.rs
index d6fc20545..e4e4c2308 100644
--- a/src/postings/intersection.rs
+++ b/src/postings/intersection.rs
@@ -2,8 +2,6 @@ use postings::DocSet;
 use postings::SkipResult;
 use DocId;
 
-// TODO Find a way to specialize `IntersectionDocSet`
-
 /// Creates a `DocSet` that iterator through the intersection of two `DocSet`s.
 pub struct IntersectionDocSet {
     docsets: Vec,
diff --git a/src/postings/mod.rs b/src/postings/mod.rs
index 60446eef6..3f196c43d 100644
--- a/src/postings/mod.rs
+++ b/src/postings/mod.rs
@@ -9,17 +9,14 @@ mod recorder;
 mod serializer;
 mod postings_writer;
 mod term_info;
-mod chained_postings;
 mod vec_postings;
 mod segment_postings;
 mod intersection;
-mod offset_postings;
 mod freq_handler;
 mod docset;
 mod segment_postings_option;
 
 pub use self::docset::{SkipResult, DocSet};
-pub use self::offset_postings::OffsetPostings;
 pub use self::recorder::{Recorder, NothingRecorder, TermFrequencyRecorder, TFAndPositionRecorder};
 pub use self::serializer::PostingsSerializer;
 pub use self::postings_writer::PostingsWriter;
@@ -29,11 +26,10 @@ pub use self::postings::Postings;
 
 #[cfg(test)]
 pub use self::vec_postings::VecPostings;
-pub use self::chained_postings::ChainedPostings;
+// pub use self::chained_postings::ChainedPostings;
 pub use self::segment_postings::{SegmentPostings, BlockSegmentPostings};
 pub use self::intersection::IntersectionDocSet;
 pub use self::freq_handler::FreqHandler;
-
 pub use self::segment_postings_option::SegmentPostingsOption;
 pub use common::HasLen;
 
@@ -51,6 +47,7 @@ mod tests {
     use query::TermQuery;
     use schema::Field;
     use test::Bencher;
+    use indexer::operation::AddOperation;
     use rand::{XorShiftRng, Rng, SeedableRng};
     
         
@@ -63,7 +60,7 @@ mod tests {
         let mut segment = index.new_segment();
         let mut posting_serializer = PostingsSerializer::open(&mut segment).unwrap();
         let term = Term::from_field_text(text_field, "abc");
-        posting_serializer.new_term(&term, 3).unwrap();
+        posting_serializer.new_term(&term).unwrap();
         for doc_id in 0u32..3u32 {
             let positions = vec!(1,2,3,2);
             posting_serializer.write_doc(doc_id, 2, &positions).unwrap();
@@ -88,19 +85,31 @@ mod tests {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "a b a c a d a a.");
                 doc.add_text(text_field, "d d d d a"); // checking that position works if the field has two values.
-                segment_writer.add_document(&doc, &schema).unwrap();
+                let op = AddOperation {
+                    opstamp: 0u64,
+                    document: doc,  
+                };
+                segment_writer.add_document(&op, &schema).unwrap();
             }
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "b a");
-                segment_writer.add_document(&doc, &schema).unwrap();
+                let op = AddOperation {
+                    opstamp: 1u64,
+                    document: doc,  
+                };
+                segment_writer.add_document(&op, &schema).unwrap();
             }
             for i in 2..1000 {
                 let mut doc = Document::default();
                 let mut text = iter::repeat("e ").take(i).collect::();
                 text.push_str(" a");
                 doc.add_text(text_field, &text);
-                segment_writer.add_document(&doc, &schema).unwrap();
+                let op = AddOperation {
+                    opstamp: 2u64,
+                    document: doc,  
+                };
+                segment_writer.add_document(&op, &schema).unwrap();
             }
             segment_writer.finalize().unwrap();
         }
@@ -167,15 +176,16 @@ mod tests {
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "g b b d c g c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {
                 let mut doc = Document::default();
                 doc.add_text(text_field, "g a b b a d c g c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             assert!(index_writer.commit().is_ok());
         }
+        index.load_searchers().unwrap();
         let term_query = TermQuery::new(Term::from_field_text(text_field, "a"), SegmentPostingsOption::NoFreq);
         let searcher = index.searcher();
         let mut term_weight = term_query.specialized_weight(&*searcher);
@@ -248,10 +258,11 @@ mod tests {
                         count_b += 1;
                         doc.add_text(text_field, "b");
                     }
-                    index_writer.add_document(doc).unwrap();
+                    index_writer.add_document(doc);
                 }
                 assert!(index_writer.commit().is_ok());
             }
+            index.load_searchers().unwrap();
             index
         };
     }
@@ -281,7 +292,6 @@ mod tests {
     fn bench_segment_intersection(b: &mut Bencher) {
         let searcher = INDEX.searcher();
         let segment_reader = searcher.segment_reader(0);
-        
         b.iter(|| {
             let segment_postings_a = segment_reader.read_postings(&*TERM_A, SegmentPostingsOption::NoFreq).unwrap();
             let segment_postings_b = segment_reader.read_postings(&*TERM_B, SegmentPostingsOption::NoFreq).unwrap();
diff --git a/src/postings/offset_postings.rs b/src/postings/offset_postings.rs
deleted file mode 100644
index 1410ef922..000000000
--- a/src/postings/offset_postings.rs
+++ /dev/null
@@ -1,59 +0,0 @@
-use postings::Postings;
-use postings::SegmentPostings;
-use postings::SkipResult;
-use postings::DocSet;
-use postings::HasLen;
-use DocId;
-
-/// Wraps a posting object and offset all of the doc id with a given offset.
-///
-/// Assuming the original posting list is `0, 5, 7, 8...`, and the offset is `3`
-/// the `OffsetPostings` becomes  `3, 8, 10, 11...`.
-pub struct OffsetPostings<'a> {
-    underlying: SegmentPostings<'a>,
-    offset: DocId,
-}
-
-impl<'a> OffsetPostings<'a> {
-    /// Constructor
-    pub fn new(underlying: SegmentPostings<'a>, offset: DocId) -> OffsetPostings {
-        OffsetPostings {
-            underlying: underlying,
-            offset: offset,
-        }
-    }
-}
-
-impl<'a> DocSet for OffsetPostings<'a> {
-    fn advance(&mut self) -> bool {
-        self.underlying.advance()
-    }
-
-    fn doc(&self) -> DocId {
-        self.underlying.doc() + self.offset
-    }
-
-    fn skip_next(&mut self, target: DocId) -> SkipResult {
-        if target >= self.offset {
-            SkipResult::OverStep
-        } else {
-            self.underlying.skip_next(target - self.offset)
-        }
-    }
-}
-
-impl<'a> HasLen for OffsetPostings<'a> {
-    fn len(&self) -> usize {
-        self.underlying.len()
-    }
-}
-
-impl<'a> Postings for OffsetPostings<'a> {
-    fn term_freq(&self) -> u32 {
-        self.underlying.term_freq()
-    }
-
-    fn positions(&self) -> &[u32] {
-        self.underlying.positions()
-    }
-}
\ No newline at end of file
diff --git a/src/postings/postings_writer.rs b/src/postings/postings_writer.rs
index c3d1f997f..0ec5559dd 100644
--- a/src/postings/postings_writer.rs
+++ b/src/postings/postings_writer.rs
@@ -22,7 +22,7 @@ pub trait PostingsWriter {
     /// * heap - heap used to store the postings informations as well as the terms
     /// in the hashmap.
     fn suscribe(&mut self, doc: DocId, pos: u32, term: &Term, heap: &Heap);
-
+    
     /// Serializes the postings on disk.
     /// The actual serialization format is handled by the `PostingsSerializer`.
     fn serialize(&self, serializer: &mut PostingsSerializer, heap: &Heap) -> io::Result<()>;
@@ -99,6 +99,7 @@ impl<'a, Rec: Recorder + 'static> PostingsWriter for SpecializedPostingsWriter<'
         }
     }
 
+
     #[inline]
     fn suscribe(&mut self, doc: DocId, position: u32, term: &Term, heap: &Heap) {
         let mut recorder = self.term_index.get_or_create(term);
@@ -119,9 +120,9 @@ impl<'a, Rec: Recorder + 'static> PostingsWriter for SpecializedPostingsWriter<'
         term_offsets.sort_by_key(|&(k, _v)| k);
         let mut term = Term::allocate(Field(0), 100);
         for (term_bytes, (addr, recorder)) in term_offsets {
-            // TODO remove copy
+            // sadly we are required to copy the data
             term.set_content(term_bytes);
-            try!(serializer.new_term(&term, recorder.doc_freq()));
+            try!(serializer.new_term(&term));
             try!(recorder.serialize(addr, serializer, heap));
             try!(serializer.close_term());
         }
diff --git a/src/postings/recorder.rs b/src/postings/recorder.rs
index 94173720b..05586858a 100644
--- a/src/postings/recorder.rs
+++ b/src/postings/recorder.rs
@@ -26,8 +26,6 @@ pub trait Recorder: HeapAllocable {
     fn record_position(&mut self, position: u32, heap: &Heap);
     /// Close the document. It will help record the term frequency.
     fn close_doc(&mut self, heap: &Heap);
-    /// Returns the number of document that have been seen so far
-    fn doc_freq(&self) -> u32;
     /// Pushes the postings information to the serializer.
     fn serialize(&self,
                  self_addr: u32,
@@ -41,7 +39,6 @@ pub trait Recorder: HeapAllocable {
 pub struct NothingRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
-    doc_freq: u32,
 }
 
 impl HeapAllocable for NothingRecorder {
@@ -49,7 +46,6 @@ impl HeapAllocable for NothingRecorder {
         NothingRecorder {
             stack: ExpUnrolledLinkedList::with_addr(addr),
             current_doc: u32::max_value(),
-            doc_freq: 0u32,
         }
     }
 }
@@ -62,17 +58,12 @@ impl Recorder for NothingRecorder {
     fn new_doc(&mut self, doc: DocId, heap: &Heap) {
         self.current_doc = doc;
         self.stack.push(doc, heap);
-        self.doc_freq += 1;
     }
 
     fn record_position(&mut self, _position: u32, _heap: &Heap) {}
 
     fn close_doc(&mut self, _heap: &Heap) {}
 
-    fn doc_freq(&self) -> u32 {
-        self.doc_freq
-    }
-
     fn serialize(&self,
                  self_addr: u32,
                  serializer: &mut PostingsSerializer,
@@ -91,7 +82,6 @@ pub struct TermFrequencyRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
     current_tf: u32,
-    doc_freq: u32,
 }
 
 impl HeapAllocable for TermFrequencyRecorder {
@@ -100,7 +90,6 @@ impl HeapAllocable for TermFrequencyRecorder {
             stack: ExpUnrolledLinkedList::with_addr(addr),
             current_doc: u32::max_value(),
             current_tf: 0u32,
-            doc_freq: 0u32,
         }
     }
 }
@@ -111,7 +100,6 @@ impl Recorder for TermFrequencyRecorder {
     }
 
     fn new_doc(&mut self, doc: DocId, heap: &Heap) {
-        self.doc_freq += 1u32;
         self.current_doc = doc;
         self.stack.push(doc, heap);
     }
@@ -126,10 +114,6 @@ impl Recorder for TermFrequencyRecorder {
         self.current_tf = 0;
     }
 
-    fn doc_freq(&self) -> u32 {
-        self.doc_freq
-    }
-
     fn serialize(&self,
                  self_addr: u32,
                  serializer: &mut PostingsSerializer,
@@ -154,7 +138,6 @@ impl Recorder for TermFrequencyRecorder {
 pub struct TFAndPositionRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
-    doc_freq: u32,
 }
 
 impl HeapAllocable for TFAndPositionRecorder {
@@ -162,7 +145,6 @@ impl HeapAllocable for TFAndPositionRecorder {
         TFAndPositionRecorder {
             stack: ExpUnrolledLinkedList::with_addr(addr),
             current_doc: u32::max_value(),
-            doc_freq: 0u32,
         }
     }
 }
@@ -173,7 +155,6 @@ impl Recorder for TFAndPositionRecorder {
     }
 
     fn new_doc(&mut self, doc: DocId, heap: &Heap) {
-        self.doc_freq += 1;
         self.current_doc = doc;
         self.stack.push(doc, heap);
     }
@@ -186,10 +167,6 @@ impl Recorder for TFAndPositionRecorder {
         self.stack.push(POSITION_END, heap);
     }
 
-    fn doc_freq(&self) -> u32 {
-        self.doc_freq
-    }
-
     fn serialize(&self,
                  self_addr: u32,
                  serializer: &mut PostingsSerializer,
diff --git a/src/postings/segment_postings.rs b/src/postings/segment_postings.rs
index 2b0606dd1..0a5412dbf 100644
--- a/src/postings/segment_postings.rs
+++ b/src/postings/segment_postings.rs
@@ -2,6 +2,7 @@ use compression::{NUM_DOCS_PER_BLOCK, BlockDecoder, VIntDecoder};
 use DocId;
 use postings::{Postings, FreqHandler, DocSet, HasLen};
 use std::num::Wrapping;
+use fastfield::delete::DeleteBitSet;
 
 
 const EMPTY_DATA: [u8; 0] = [0u8; 0];
@@ -85,10 +86,10 @@ impl<'a> BlockSegmentPostings<'a> {
 /// Positions on the other hand, are optionally entirely decoded upfront.
 pub struct SegmentPostings<'a> {
     len: usize,
-    // doc_offset: usize,
     cur: Wrapping,
     block_cursor: BlockSegmentPostings<'a>,
-    cur_block_len: usize
+    cur_block_len: usize,
+    delete_bitset: DeleteBitSet,
 }
 
 impl<'a> SegmentPostings<'a> {
@@ -99,12 +100,15 @@ impl<'a> SegmentPostings<'a> {
     /// * `data` - data array. The complete data is not necessarily used.
     /// * `freq_handler` - the freq handler is in charge of decoding
     ///   frequencies and/or positions
-    pub fn from_block_postings(segment_block_postings: BlockSegmentPostings<'a>) -> SegmentPostings<'a> {
+    pub fn from_block_postings(
+            segment_block_postings: BlockSegmentPostings<'a>,
+            delete_bitset: DeleteBitSet) -> SegmentPostings<'a> {
         SegmentPostings {
             len: segment_block_postings.len,
             block_cursor: segment_block_postings,
             cur: Wrapping(usize::max_value()),
             cur_block_len: 0,
+            delete_bitset: delete_bitset,
         }
     }
     
@@ -114,6 +118,7 @@ impl<'a> SegmentPostings<'a> {
         SegmentPostings {
             len: 0,
             block_cursor: empty_block_cursor,
+            delete_bitset: DeleteBitSet::empty(),
             cur: Wrapping(usize::max_value()),
             cur_block_len: 0,
         }
@@ -126,17 +131,21 @@ impl<'a> DocSet for SegmentPostings<'a> {
     // next needs to be called a first time to point to the correct element.
     #[inline]
     fn advance(&mut self) -> bool {
-        self.cur += Wrapping(1);
-        if self.cur.0 == self.cur_block_len {
-            self.cur = Wrapping(0);
-            if !self.block_cursor.advance() {
-                self.cur_block_len = 0;
-                self.cur = Wrapping(usize::max_value());
-                return false;
+        loop {   
+            self.cur += Wrapping(1);
+            if self.cur.0 == self.cur_block_len {
+                self.cur = Wrapping(0);
+                if !self.block_cursor.advance() {
+                    self.cur_block_len = 0;
+                    self.cur = Wrapping(usize::max_value());
+                    return false;
+                }
+                self.cur_block_len = self.block_cursor.docs().len();
+            }
+            if !self.delete_bitset.is_deleted(self.doc()) {
+                return true;
             }
-            self.cur_block_len = self.block_cursor.docs().len();
         }
-        true
     }
 
     #[inline]
diff --git a/src/postings/serializer.rs b/src/postings/serializer.rs
index db520c15e..238559640 100644
--- a/src/postings/serializer.rs
+++ b/src/postings/serializer.rs
@@ -49,7 +49,7 @@ use common::BinarySerializable;
 /// A description of the serialization format is
 /// [available here](https://fulmicoton.gitbooks.io/tantivy-doc/content/inverted-index.html).
 pub struct PostingsSerializer {
-    terms_fst_builder: TermDictionaryBuilder, /* TODO find an alternative to work around the "move" */
+    terms_fst_builder: TermDictionaryBuilder, 
     postings_write: WritePtr,
     positions_write: WritePtr,
     written_bytes_postings: usize,
@@ -63,6 +63,7 @@ pub struct PostingsSerializer {
     schema: Schema,
     text_indexing_options: TextIndexingOptions,
     term_open: bool,
+    current_term_info: TermInfo,
 }
 
 impl PostingsSerializer {
@@ -88,6 +89,7 @@ impl PostingsSerializer {
             schema: schema,
             text_indexing_options: TextIndexingOptions::Unindexed,
             term_open: false,
+            current_term_info: TermInfo::default(),
         })
     }
 
@@ -121,7 +123,7 @@ impl PostingsSerializer {
     /// * term - the term. It needs to come after the previous term according
     ///   to the lexicographical order.
     /// * doc_freq - return the number of document containing the term.
-    pub fn new_term(&mut self, term: &Term, doc_freq: DocId) -> io::Result<()> {
+    pub fn new_term(&mut self, term: &Term) -> io::Result<()> {
         if self.term_open {
             panic!("Called new_term, while the previous term was not closed.");
         }
@@ -131,13 +133,12 @@ impl PostingsSerializer {
         self.last_doc_id_encoded = 0;
         self.term_freqs.clear();
         self.position_deltas.clear();
-        let term_info = TermInfo {
-            doc_freq: doc_freq,
+        self.current_term_info = TermInfo {
+            doc_freq: 0,
             postings_offset: self.written_bytes_postings as u32,
             positions_offset: self.written_bytes_positions as u32,
         };
-        self.terms_fst_builder
-            .insert(term.as_slice(), &term_info)
+        self.terms_fst_builder.insert_key(term.as_slice())
     }
 
     /// Finish the serialization for this term postings.
@@ -146,6 +147,9 @@ impl PostingsSerializer {
     /// using `VInt` encoding.
     pub fn close_term(&mut self) -> io::Result<()> {
         if self.term_open {
+
+            self.terms_fst_builder.insert_value(&self.current_term_info)?;
+
             if !self.doc_ids.is_empty() {
                 // we have doc ids waiting to be written
                 // this happens when the number of doc ids is
@@ -202,6 +206,7 @@ impl PostingsSerializer {
                      term_freq: u32,
                      position_deltas: &[u32])
                      -> io::Result<()> {
+        self.current_term_info.doc_freq += 1;
         self.doc_ids.push(doc_id);
         if self.text_indexing_options.is_termfreq_enabled() {
             self.term_freqs.push(term_freq as u32);
diff --git a/src/postings/term_info.rs b/src/postings/term_info.rs
index 87ff9b62e..c268ca850 100644
--- a/src/postings/term_info.rs
+++ b/src/postings/term_info.rs
@@ -12,7 +12,7 @@ use std::io;
 /// * `postings_offset` : an offset in the `.idx` file 
 /// addressing the start of the posting list associated
 /// to this term.
-#[derive(Debug,Ord,PartialOrd,Eq,PartialEq,Clone)]
+#[derive(Debug,Default,Ord,PartialOrd,Eq,PartialEq,Clone)]
 pub struct TermInfo {
     /// Number of documents in the segment containing the term
     pub doc_freq: u32,
@@ -22,15 +22,6 @@ pub struct TermInfo {
     pub positions_offset: u32,
 }
 
-impl Default for TermInfo {
-    fn default() -> TermInfo {
-        TermInfo {
-            doc_freq: 0u32,
-            postings_offset: 0u32,
-            positions_offset: 0u32,
-        }
-    }
-}
 
 impl BinarySerializable for TermInfo {
     fn serialize(&self, writer: &mut io::Write) -> io::Result {
diff --git a/src/query/boolean_query/mod.rs b/src/query/boolean_query/mod.rs
index 7ed352170..1b41a8996 100644
--- a/src/query/boolean_query/mod.rs
+++ b/src/query/boolean_query/mod.rs
@@ -8,3 +8,138 @@ pub use self::boolean_scorer::BooleanScorer;
 pub use self::score_combiner::ScoreCombiner;
 
 
+
+#[cfg(test)]
+mod tests {
+    
+    use super::*;
+    use postings::{DocSet, VecPostings};
+    use query::Scorer;
+    use query::OccurFilter;
+    use query::term_query::TermScorer;
+    use query::Occur;
+    use query::Query;
+    use query::TermQuery;
+    use collector::tests::TestCollector;
+    use Index;
+    use schema::*;
+    use fastfield::{U32FastFieldReader};
+    use postings::SegmentPostingsOption;
+
+    fn abs_diff(left: f32, right: f32) -> f32 {
+        (right - left).abs()
+    }   
+
+
+    #[test]
+    pub fn test_boolean_query() {
+        let mut schema_builder = SchemaBuilder::default();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+        let index = Index::create_from_tempdir(schema).unwrap();
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            {
+                let doc = doc!(text_field => "a b c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "a c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "b c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "a b c d");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "d");
+                index_writer.add_document(doc);
+            }
+            assert!(index_writer.commit().is_ok());
+        }
+
+        let make_term_query = |text: &str| {
+            let term_query = TermQuery::new(Term::from_field_text(text_field, text), SegmentPostingsOption::NoFreq);
+            let query: Box = box term_query;
+            query
+        };
+
+        index.load_searchers().unwrap();
+
+        let matching_docs = |boolean_query: &Query| {
+            let searcher = index.searcher();
+            let mut test_collector = TestCollector::default();
+            searcher.search(boolean_query, &mut test_collector).unwrap();
+            test_collector.docs()
+        };
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::Must, make_term_query("a")) ]);
+            assert_eq!(matching_docs(&boolean_query), vec!(0, 1, 3));
+        }
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::Should, make_term_query("a")) ]);
+            assert_eq!(matching_docs(&boolean_query), vec!(0, 1, 3));
+        }
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::Should, make_term_query("a")),  (Occur::Should, make_term_query("b"))]);
+            assert_eq!(matching_docs(&boolean_query), vec!(0, 1, 2, 3));
+        }
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::Must, make_term_query("a")),  (Occur::Should, make_term_query("b"))]);
+            assert_eq!(matching_docs(&boolean_query), vec!(0, 1, 3));
+        }
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::Must, make_term_query("a")), 
+                                                        (Occur::Should, make_term_query("b")),
+                                                        (Occur::MustNot, make_term_query("d")),
+                                                        ]);
+            assert_eq!(matching_docs(&boolean_query), vec!(0, 1));
+        }
+        {
+            let boolean_query = BooleanQuery::from(vec![(Occur::MustNot, make_term_query("d")),]);
+            assert_eq!(matching_docs(&boolean_query), Vec::new());
+        }
+    }
+
+    #[test]
+    pub fn test_boolean_scorer() {
+        let occurs = vec!(Occur::Should, Occur::Should);
+        let occur_filter = OccurFilter::new(&occurs);
+       
+        let left_fieldnorms = U32FastFieldReader::from(vec!(100,200,300));
+        
+        let left = VecPostings::from(vec!(1, 2, 3));
+        let left_scorer = TermScorer {
+            idf: 1f32,
+            fieldnorm_reader_opt: Some(left_fieldnorms),
+            postings: left,
+        };
+        
+        let right_fieldnorms = U32FastFieldReader::from(vec!(15,25,35));
+        let right = VecPostings::from(vec!(1, 3, 8));
+        
+        let right_scorer = TermScorer {
+            idf: 4f32,
+            fieldnorm_reader_opt: Some(right_fieldnorms),
+            postings: right,
+        };
+
+        let mut boolean_scorer = BooleanScorer::new(vec!(left_scorer, right_scorer), occur_filter);
+        assert_eq!(boolean_scorer.next(), Some(1u32));
+        assert!(abs_diff(boolean_scorer.score(), 0.8707107) < 0.001);
+        assert_eq!(boolean_scorer.next(), Some(2u32));
+        assert!(abs_diff(boolean_scorer.score(), 0.028867513) < 0.001f32);
+        assert_eq!(boolean_scorer.next(), Some(3u32));
+        assert_eq!(boolean_scorer.next(), Some(8u32));
+        assert!(abs_diff(boolean_scorer.score(), 0.5163978) < 0.001f32);
+        assert!(!boolean_scorer.advance());
+    }
+    
+    
+
+}
diff --git a/src/query/phrase_query/mod.rs b/src/query/phrase_query/mod.rs
index 6983ff65e..4c9d1dca0 100644
--- a/src/query/phrase_query/mod.rs
+++ b/src/query/phrase_query/mod.rs
@@ -27,27 +27,28 @@ mod tests {
             let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
             {   // 0
                 let doc = doc!(text_field=>"b b b d c g c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {   // 1
                 let doc = doc!(text_field=>"a b b d c g c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {   // 2
                 let doc = doc!(text_field=>"a b a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {   // 3
                 let doc = doc!(text_field=>"c a b a d ga a");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             {   // 4
                 let doc = doc!(text_field=>"a b c");
-                index_writer.add_document(doc).unwrap();
+                index_writer.add_document(doc);
             }
             assert!(index_writer.commit().is_ok());
         }
 
+        index.load_searchers().unwrap();
         let searcher = index.searcher();
         let test_query = |texts: Vec<&str>| {
             let mut test_collector = TestCollector::default();
diff --git a/src/query/term_query/mod.rs b/src/query/term_query/mod.rs
index e8be286c1..8aa56484a 100644
--- a/src/query/term_query/mod.rs
+++ b/src/query/term_query/mod.rs
@@ -5,3 +5,67 @@ mod term_scorer;
 pub use self::term_query::TermQuery;
 pub use self::term_weight::TermWeight;
 pub use self::term_scorer::TermScorer;
+
+
+#[cfg(test)]
+mod tests {
+    
+    use postings::{DocSet, VecPostings};
+    use query::Scorer;
+    use query::term_query::TermScorer;
+    use query::Query;
+    use fastfield::U32FastFieldReader;
+    use query::TermQuery;
+    use Index;
+    use schema::*;
+    use postings::SegmentPostingsOption;
+
+    fn abs_diff(left: f32, right: f32) -> f32 {
+        (right - left).abs()
+    }   
+
+
+    #[test]
+    pub fn test_term_query_no_freq() {
+        let mut schema_builder = SchemaBuilder::default();
+        let text_field = schema_builder.add_text_field("text", STRING);
+        let schema = schema_builder.build();
+        let index = Index::create_from_tempdir(schema).unwrap();
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            {
+                let doc = doc!(text_field => "a");
+                index_writer.add_document(doc);
+            }
+            assert!(index_writer.commit().is_ok());
+        }
+
+        index.load_searchers().unwrap();
+        let searcher = index.searcher();
+        let term_query = TermQuery::new(Term::from_field_text(text_field, "a"), SegmentPostingsOption::NoFreq);
+        let term_weight = term_query.weight(&searcher).unwrap();
+        let segment_reader = searcher.segment_reader(0);
+        let mut term_scorer = term_weight.scorer(segment_reader).unwrap();
+        assert!(term_scorer.advance());
+        assert_eq!(term_scorer.doc(), 0);
+        assert_eq!(term_scorer.score(), 0.30685282);
+    }
+
+       
+    #[test]
+    pub fn test_term_scorer() {
+        let left_fieldnorms = U32FastFieldReader::from(vec!(10, 4));
+        assert_eq!(left_fieldnorms.get(0), 10);
+        assert_eq!(left_fieldnorms.get(1), 4);
+        let left = VecPostings::from(vec!(1));
+        let mut left_scorer = TermScorer {
+            idf: 0.30685282,
+            fieldnorm_reader_opt: Some(left_fieldnorms),
+            postings: left,
+        };
+        left_scorer.advance();
+        assert!(abs_diff(left_scorer.score(), 0.15342641) < 0.001f32);
+    }
+
+}
\ No newline at end of file
diff --git a/src/query/term_query/term_scorer.rs b/src/query/term_query/term_scorer.rs
index cf679fb4d..81b683c99 100644
--- a/src/query/term_query/term_scorer.rs
+++ b/src/query/term_query/term_scorer.rs
@@ -6,6 +6,8 @@ use query::Scorer;
 use postings::Postings;
 
 pub struct TermScorer where TPostings: Postings {
+    pub idf: Score,
+    pub fieldnorm_reader_opt: Option,
     pub postings: TPostings,
 }
 
@@ -27,7 +29,17 @@ impl DocSet for TermScorer where TPostings: Postings {
 
 impl Scorer for TermScorer where TPostings: Postings {
     fn score(&self,) -> Score {
-        1.0
+        let doc = self.postings.doc();
+        let tf = match self.fieldnorm_reader_opt {
+            Some(ref fieldnorm_reader) => {
+                let field_norm = fieldnorm_reader.get(doc);
+                (self.postings.term_freq() as f32 / field_norm as f32)
+            }
+            None => {
+                self.postings.term_freq() as f32
+            }
+        };
+        self.idf * tf.sqrt()
     } 
 }
 
diff --git a/src/query/term_query/term_weight.rs b/src/query/term_query/term_weight.rs
index bb9752786..48a000755 100644
--- a/src/query/term_query/term_weight.rs
+++ b/src/query/term_query/term_weight.rs
@@ -4,7 +4,6 @@ use core::SegmentReader;
 use query::Scorer;
 use postings::SegmentPostingsOption;
 use postings::SegmentPostings;
-use fastfield::U32FastFieldReader;
 use super::term_scorer::TermScorer;
 use Result;
 
@@ -33,17 +32,21 @@ impl TermWeight {
 
     pub fn specialized_scorer<'a>(&'a self, reader: &'a SegmentReader) -> Result>> {
         let field = self.term.field();
-        // let fieldnorm_reader = try!(reader.get_fieldnorms_reader(field));
+        let fieldnorm_reader_opt = reader.get_fieldnorms_reader(field);
         Ok(
             reader
                 .read_postings(&self.term, self.segment_postings_options)
                 .map(|segment_postings|
                     TermScorer {
+                        idf: self.idf(),
+                        fieldnorm_reader_opt: fieldnorm_reader_opt,
                         postings: segment_postings,
                     }
                 )
                 .unwrap_or(
                     TermScorer {
+                        idf: 1f32,
+                        fieldnorm_reader_opt: None,
                         postings: SegmentPostings::empty()
                     })
         )
diff --git a/src/schema/document.rs b/src/schema/document.rs
index 671237155..87d0b46f7 100644
--- a/src/schema/document.rs
+++ b/src/schema/document.rs
@@ -11,7 +11,7 @@ use itertools::Itertools;
 
 /// Documents are really just a list of couple `(field, value)`.
 /// In this list, one field may appear more than once.
-#[derive(Debug, RustcEncodable, RustcDecodable)]
+#[derive(Debug, RustcEncodable, RustcDecodable, Default)]
 pub struct Document {
     field_values: Vec,
 }
@@ -31,6 +31,11 @@ impl Eq for Document {}
 
 impl Document {
     
+    /// Creates a new, empty document object
+    pub fn new() -> Document {
+        Document::default()
+    }
+
     /// Returns the number of `(field, value)` pairs.
     pub fn len(&self,) -> usize {
         self.field_values.len()
@@ -97,14 +102,6 @@ impl Document {
     }
 }
 
-impl Default for Document {
-    
-    fn default() -> Document {
-        Document {
-            field_values: Vec::new(),
-        }
-    }
-}
 
 impl From> for Document {
     fn from(field_values: Vec) -> Document {
diff --git a/src/schema/field_entry.rs b/src/schema/field_entry.rs
index 253d2ebb0..99f3cb42c 100644
--- a/src/schema/field_entry.rs
+++ b/src/schema/field_entry.rs
@@ -54,7 +54,7 @@ impl FieldEntry {
     pub fn is_indexed(&self,) -> bool {
         match self.field_type {
             FieldType::Str(ref options) => options.get_indexing_options().is_indexed(),
-            _ => false, // TODO handle u32 indexed
+            FieldType::U32(ref options) => options.is_indexed(),
         }
     }
     
diff --git a/src/schema/mod.rs b/src/schema/mod.rs
index 224d9f47d..b1802d1e5 100644
--- a/src/schema/mod.rs
+++ b/src/schema/mod.rs
@@ -131,6 +131,8 @@ pub use self::text_options::STORED;
 
 pub use self::u32_options::U32Options;
 pub use self::u32_options::FAST;
+pub use self::u32_options::U32_INDEXED;
+pub use self::u32_options::U32_STORED;
 
 use regex::Regex;
 
diff --git a/src/schema/schema.rs b/src/schema/schema.rs
index bdd699eea..3ed8b6c9d 100644
--- a/src/schema/schema.rs
+++ b/src/schema/schema.rs
@@ -12,7 +12,7 @@ use std::sync::Arc;
 use super::*;
 use std::fmt;
 
-
+const MAX_NUM_FIELDS: usize = 255;
 
 /// Tantivy has a very strict schema.
 /// You need to specify in advance whether a field is indexed or not,
@@ -42,6 +42,12 @@ pub struct SchemaBuilder {
 
 impl SchemaBuilder {
     
+
+    /// Create a new `SchemaBuilder`
+    pub fn new() -> SchemaBuilder {
+        SchemaBuilder::default()
+    }
+
     /// Adds a new u32 field.
     /// Returns the associated field handle
     ///
@@ -94,10 +100,13 @@ impl SchemaBuilder {
     /// Finalize the creation of a `Schema`
     /// This will consume your `SchemaBuilder`
     pub fn build(self,) -> Schema {
+        if self.fields.len() > MAX_NUM_FIELDS {
+            panic!("There may be at most 255 fields.");
+        }
         Schema(Arc::new(InnerSchema {
             fields: self.fields,
             fields_map: self.fields_map,
-        })) 
+        }))
     }
 }
 
@@ -329,7 +338,6 @@ mod tests {
         schema_builder.add_u32_field("count", count_options);
         let schema = schema_builder.build();
         let schema_json: String = format!("{}", json::as_pretty_json(&schema));
-        println!("{}", schema_json);
         let expected = r#"[
   {
     "name": "title",
@@ -456,7 +464,6 @@ mod tests {
                 "author": "fulmicoton",
                 "count": -5
             }"#);
-            println!("{:?}", json_err);
             match json_err {
                 Err(DocParsingError::ValueError(_, ValueParsingError::TypeError(_))) => {
                     assert!(true);
@@ -472,7 +479,6 @@ mod tests {
                 "author": "fulmicoton",
                 "count": 5000000000
             }"#);
-            println!("{:?}", json_err);
             match json_err {
                 Err(DocParsingError::ValueError(_, ValueParsingError::OverflowError(_))) => {
                     assert!(true);
diff --git a/src/schema/term.rs b/src/schema/term.rs
index 305aac6b6..f5502e00e 100644
--- a/src/schema/term.rs
+++ b/src/schema/term.rs
@@ -1,6 +1,8 @@
 use std::fmt;
 
 use common::BinarySerializable;
+use common::allocate_vec;
+use byteorder::{BigEndian, ByteOrder};
 use super::Field;
 use std::str;
 
@@ -11,7 +13,6 @@ use std::str;
 #[derive(Clone, PartialEq, PartialOrd, Ord, Eq, Hash)]
 pub struct Term(Vec);
 
-
 impl Term {
     
     /// Pre-allocate a term buffer. 
@@ -43,10 +44,12 @@ impl Term {
     /// the Term will have 5 bytes.
     /// The first byte is `1`, and the 4 following bytes are that of the u32.
     pub fn from_field_u32(field: Field, val: u32) -> Term {
-        let mut buffer = Vec::with_capacity(1 + 4);
-        buffer.clear();
-        field.serialize(&mut buffer).unwrap();
-        val.serialize(&mut buffer).unwrap();
+        const U32_TERM_LEN: usize = 1 + 4;
+        let mut buffer = allocate_vec(U32_TERM_LEN);
+        buffer[0] = field.0;
+        // we want BigEndian here to have lexicographic order
+        // match the natural order of vals.
+        BigEndian::write_u32(&mut buffer[1..5], val);
         Term(buffer)
     }
     
@@ -63,7 +66,22 @@ impl Term {
         buffer.extend(text.as_bytes());
         Term(buffer)
     }
+
+    /// Assume the term is a u32 field.
+    ///
+    /// Panics if the term is not a u32 field.
+    pub fn get_u32(&self) -> u32 {
+        BigEndian::read_u32(&self.0[1..])
+    }
     
+    /// Builds a term from its byte representation.
+    ///
+    /// If you want to build a field for a given `str`,
+    /// you want to use `from_field_text`.
+    pub fn from_bytes(data: &[u8]) -> Term {
+        Term(Vec::from(data))
+    }
+
     /// Returns the serialized value of the term.
     /// (this does not include the field.)
     ///
@@ -96,12 +114,6 @@ impl Term {
     }
 }
 
-impl<'a> From<&'a [u8]> for Term {
-    fn from(data: &[u8]) -> Term {
-        Term(Vec::from(data))
-    }
-}
-
 impl AsRef<[u8]> for Term {
     fn as_ref(&self) -> &[u8] {
         &self.0
@@ -115,7 +127,6 @@ impl fmt::Debug for Term {
 }
 
 
-
 #[cfg(test)]
 mod tests {
     
@@ -138,7 +149,10 @@ mod tests {
             assert_eq!(term.field(), count_field);
             assert_eq!(term.as_slice()[0], 2u8);
             assert_eq!(term.as_slice().len(), 5);
-            assert_eq!(term.as_slice()[1], (983u32 % 256u32) as u8);            
+            assert_eq!(term.as_slice()[1], 0u8);
+            assert_eq!(term.as_slice()[2], 0u8);
+            assert_eq!(term.as_slice()[3], (933u32 / 256u32) as u8);
+            assert_eq!(term.as_slice()[4], (983u32 % 256u32) as u8);
         }
                 
     }
diff --git a/src/schema/text_options.rs b/src/schema/text_options.rs
index 91000de81..c718e2a87 100644
--- a/src/schema/text_options.rs
+++ b/src/schema/text_options.rs
@@ -206,7 +206,7 @@ impl BitOr for TextOptions {
     fn bitor(self, other: TextOptions) -> TextOptions {
         let mut res = TextOptions::default();
         res.indexing = self.indexing | other.indexing;
-        res.stored = self.stored || other.stored;
+        res.stored = self.stored | other.stored;
         res
     }
 }
diff --git a/src/schema/u32_options.rs b/src/schema/u32_options.rs
index 39be904ed..5f29f63b5 100644
--- a/src/schema/u32_options.rs
+++ b/src/schema/u32_options.rs
@@ -1,3 +1,5 @@
+use std::ops::BitOr;
+
 /// Define how a U32 field should be handled by tantivy.
 #[derive(Clone,Debug,PartialEq,Eq, RustcDecodable, RustcEncodable)]
 pub struct U32Options {
@@ -65,9 +67,43 @@ impl Default for U32Options {
 }
 
 
-/// Shortcut for   
+/// Shortcut for a u32 fast field.
+///
+/// Such a shortcut can be composed as follows `STORED | FAST | U32_INDEXED`
 pub const FAST: U32Options = U32Options {
     indexed: false,
     stored: false,
     fast: true,
 };
+
+/// Shortcut for a u32 indexed field.
+///
+/// Such a shortcut can be composed as follows `STORED | FAST | U32_INDEXED`
+pub const U32_INDEXED: U32Options = U32Options {
+    indexed: true,
+    stored: false,
+    fast: false,
+};
+
+/// Shortcut for a u32 stored field. 
+///
+/// Such a shortcut can be composed as follows `STORED | FAST | U32_INDEXED`
+pub const U32_STORED: U32Options = U32Options {
+    indexed: false,
+    stored: true,
+    fast: false,
+};
+
+
+impl BitOr for U32Options {
+
+    type Output = U32Options;
+
+    fn bitor(self, other: U32Options) -> U32Options {
+        let mut res = U32Options::default();
+        res.indexed = self.indexed | other.indexed;
+        res.stored = self.stored | other.stored;
+        res.fast = self.fast | other.fast;
+        res
+    }
+}
\ No newline at end of file
diff --git a/src/store/reader.rs b/src/store/reader.rs
index c3bfddfb7..3a9918f9d 100644
--- a/src/store/reader.rs
+++ b/src/store/reader.rs
@@ -11,6 +11,7 @@ use std::io::{self, Read};
 use datastruct::SkipList;
 use lz4;
 
+#[derive(Clone)]
 pub struct StoreReader {
     pub data: ReadOnlySource,
     pub offset_index_source: ReadOnlySource,
diff --git a/src/store/writer.rs b/src/store/writer.rs
index 569d8f509..426648381 100644
--- a/src/store/writer.rs
+++ b/src/store/writer.rs
@@ -2,12 +2,9 @@ use directory::WritePtr;
 use DocId;
 use schema::FieldValue;
 use common::BinarySerializable;
-use std::io::Write;
-use std::io;
-use error::Result;
+use std::io::{self, Write};
 use lz4;
 use datastruct::SkipListBuilder;
-use super::StoreReader;
 
 const BLOCK_SIZE: usize = 16_384;
 
@@ -33,17 +30,6 @@ impl StoreWriter {
         }
     }
 
-    pub fn stack_reader(&mut self, reader: &StoreReader) -> Result<()> {
-        for doc_id in 0..reader.max_doc {
-            let doc = try!(reader.get(doc_id));
-            let field_values: Vec<&FieldValue> = doc.field_values()
-                .iter()
-                .collect();
-            try!(self.store(&field_values));
-        }
-        Ok(())
-    }
-
     pub fn store<'a>(&mut self, field_values: &[&'a FieldValue]) -> io::Result<()> {
         self.intermediary_buffer.clear();
         try!((field_values.len() as u32).serialize(&mut self.intermediary_buffer));