Edited changelog and bumped version.

This branch is to be published as a hotfix for 5.1.0.

Closes #280
Closes #274
Closes #289

CHANGELOG.md

@@ -1,3 +1,9 @@
+Tantivy 0.5.2
+===========================
+- bugfix #274
+- bugfix #280
+- bugfix #289
+
 Tantivy 0.5.1
 ==========================
 - bugfix #254 : tantivy failed if no documents in a segment contained a specific field.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.5.1"
+version = "0.5.2"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 build = "build.rs"
 license = "MIT"

src/core/segment_reader.rs

@@ -107,6 +107,19 @@ impl SegmentReader {
         }
     }
 
+    pub(crate) fn fast_field_reader_with_idx<Item: FastValue>(
+        &self,
+        field: Field,
+        idx: usize
+    ) -> fastfield::Result<FastFieldReader<Item>> {
+        if let Some(ff_source) = self.fast_fields_composite.open_read_with_idx(field, idx) {
+            Ok(FastFieldReader::open(ff_source))
+        } else {
+            let field_entry = self.schema.get_field_entry(field);
+            Err(FastFieldNotAvailableError::new(field_entry))
+        }
+    }
+
     /// Accessor to the `MultiValueIntFastFieldReader` associated to a given `Field`.
     /// May panick if the field is not a multivalued fastfield of the type `Item`.
     pub fn multi_fast_field_reader<Item: FastValue>(
@@ -116,14 +129,8 @@ impl SegmentReader {
         let field_entry = self.schema.get_field_entry(field);
         if Item::fast_field_cardinality(field_entry.field_type()) == Some(Cardinality::MultiValues)
         {
-            let idx_reader = self.fast_fields_composite
-                .open_read_with_idx(field, 0)
-                .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))
-                .map(FastFieldReader::open)?;
-            let vals_reader = self.fast_fields_composite
-                .open_read_with_idx(field, 1)
-                .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))
-                .map(FastFieldReader::open)?;
+            let idx_reader = self.fast_field_reader_with_idx(field, 0)?;
+            let vals_reader = self.fast_field_reader_with_idx(field, 1)?;
             Ok(MultiValueIntFastFieldReader::open(idx_reader, vals_reader))
         } else {
             Err(FastFieldNotAvailableError::new(field_entry))

src/fastfield/multivalued/reader.rs

@@ -26,13 +26,31 @@ impl<Item: FastValue> MultiValueIntFastFieldReader<Item> {
         }
     }
 
+    /// Returns `(start, stop)`, such that the values associated
+    /// to the given document are `start..stop`.
+    fn range(&self, doc: DocId) -> (u64, u64) {
+        let start = self.idx_reader.get(doc);
+        let stop = self.idx_reader.get(doc + 1);
+        (start, stop)
+    }
+
+    /// Returns the number of values associated to a given document.
+    pub fn num_vals(&self, doc: DocId) -> usize {
+        let (start, stop) = self.range(doc);
+        (stop - start) as usize
+    }
+
+    /// Returns the overall number of values associated to documents.
+    pub(crate) fn total_num_vals(&self) -> u64 {
+        self.idx_reader.max_value()
+    }
+
     /// Returns the array of values associated to the given `doc`.
     pub fn get_vals(&self, doc: DocId, vals: &mut Vec<Item>) {
-        let start = self.idx_reader.get(doc) as u32;
-        let stop = self.idx_reader.get(doc + 1) as u32;
+        let (start, stop) = self.range(doc);
         let len = (stop - start) as usize;
         vals.resize(len, Item::default());
-        self.vals_reader.get_range(start, &mut vals[..]);
+        self.vals_reader.get_range(start as u32, &mut vals[..]);
     }
 }
 

src/fastfield/multivalued/writer.rs

@@ -6,6 +6,7 @@ use postings::UnorderedTermId;
 use schema::{Document, Field};
 use std::io;
 use itertools::Itertools;
+use termdict::TermOrdinal;
 
 pub struct MultiValueIntFastFieldWriter {
     field: Field,
@@ -66,7 +67,7 @@ impl MultiValueIntFastFieldWriter {
     pub fn serialize(
         &self,
         serializer: &mut FastFieldSerializer,
-        mapping_opt: Option<&HashMap<UnorderedTermId, usize>>,
+        mapping_opt: Option<&HashMap<UnorderedTermId, TermOrdinal>>,
     ) -> io::Result<()> {
         {
             // writing the offset index
@@ -90,13 +91,13 @@ impl MultiValueIntFastFieldWriter {
                         1,
                     )?;
                     for val in &self.vals {
-                        let remapped_val = *mapping.get(val).expect("Missing term ordinal") as u64;
+                        let remapped_val = *mapping.get(val).expect("Missing term ordinal");
                         value_serializer.add_val(remapped_val)?;
                     }
                 }
                 None => {
                     let val_min_max = self.vals.iter().cloned().minmax();
-                    let (val_min, val_max) = val_min_max.into_option().unwrap_or((0u64, 0));
+                    let (val_min, val_max) = val_min_max.into_option().unwrap_or((0u64, 0u64));
                     value_serializer =
                         serializer.new_u64_fast_field_with_idx(self.field, val_min, val_max, 1)?;
                     for &val in &self.vals {

src/fastfield/reader.rs

@@ -71,6 +71,9 @@ impl<Item: FastValue> FastFieldReader<Item> {
     ///
     /// May panic if `start + output.len()` is greater than
     /// the segment's `maxdoc`.
+    ///
+    // TODO change start to `u64`.
+    // For multifastfield, start is an index in a second fastfield, not a `DocId`
     pub fn get_range(&self, start: u32, output: &mut [Item]) {
         let output_u64: &mut [u64] = unsafe { mem::transmute(output) };
         self.bit_unpacker.get_range(start, output_u64);

src/fastfield/serializer.rs

@@ -77,11 +77,21 @@ pub struct FastSingleFieldSerializer<'a, W: Write + 'a> {
 }
 
 impl<'a, W: Write> FastSingleFieldSerializer<'a, W> {
+
+    /// Creates a new fast field serializer.
+    ///
+    /// The serializer in fact encode the values by bitpacking
+    /// `(val - min_value)`.
+    ///
+    /// It requires a `min_value` and a `max_value` to compute
+    /// compute the minimum number of bits required to encode
+    /// values.
     fn open(
         write: &'a mut W,
         min_value: u64,
         max_value: u64,
     ) -> io::Result<FastSingleFieldSerializer<'a, W>> {
+        assert!(min_value <= max_value);
         min_value.serialize(write)?;
         let amplitude = max_value - min_value;
         amplitude.serialize(write)?;

src/fastfield/writer.rs

@@ -9,6 +9,7 @@ use std::collections::HashMap;
 use postings::UnorderedTermId;
 use super::multivalued::MultiValueIntFastFieldWriter;
 use common::BinarySerializable;
+use termdict::TermOrdinal;
 
 /// The fastfieldswriter regroup all of the fast field writers.
 pub struct FastFieldsWriter {
@@ -105,7 +106,7 @@ impl FastFieldsWriter {
     pub fn serialize(
         &self,
         serializer: &mut FastFieldSerializer,
-        mapping: &HashMap<Field, HashMap<UnorderedTermId, usize>>,
+        mapping: &HashMap<Field, HashMap<UnorderedTermId, TermOrdinal>>,
     ) -> io::Result<()> {
         for field_writer in &self.single_value_writers {
             field_writer.serialize(serializer)?;

src/indexer/index_writer.rs

@@ -200,7 +200,6 @@ pub fn advance_deletes(
     target_opstamp: u64,
 ) -> Result<Option<FileProtection>> {
     let mut file_protect: Option<FileProtection> = None;
-
     {
         if let Some(previous_opstamp) = segment_entry.meta().delete_opstamp() {
             // We are already up-to-date here.
@@ -241,7 +240,6 @@ pub fn advance_deletes(
         }
     }
     segment_entry.set_meta(segment.meta().clone());
-
     Ok(file_protect)
 }
 

src/indexer/merger.rs

@@ -14,9 +14,14 @@ use termdict::TermMerger;
 use fastfield::FastFieldSerializer;
 use fastfield::FastFieldReader;
 use store::StoreWriter;
-use std::cmp::{max, min};
 use termdict::TermDictionary;
 use termdict::TermStreamer;
+use schema::FieldType;
+use termdict::TermOrdinal;
+use schema::Cardinality;
+use std::collections::HashMap;
+use fastfield::MultiValueIntFastFieldReader;
+use std::cmp;
 
 pub struct IndexMerger {
     schema: Schema,
@@ -60,6 +65,43 @@ fn extract_fast_field_reader(
     segment_reader.fast_field_reader(field).ok()
 }
 
+
+struct TermOrdinalMapping {
+    per_segment_new_term_ordinals: Vec<Vec<TermOrdinal>>
+}
+
+impl TermOrdinalMapping {
+    fn new(max_term_ords: Vec<TermOrdinal>) -> TermOrdinalMapping {
+        TermOrdinalMapping {
+            per_segment_new_term_ordinals: max_term_ords
+                .into_iter()
+                .map(|max_term_ord| vec![TermOrdinal::default(); max_term_ord as usize])
+                .collect()
+        }
+    }
+
+    fn register_from_to(&mut self,
+                        segment_ord: usize,
+                        from_ord: TermOrdinal,
+                        to_ord: TermOrdinal) {
+        self.per_segment_new_term_ordinals[segment_ord][from_ord as usize] = to_ord;
+    }
+
+    fn get_segment(&self, segment_ord: usize) -> &[TermOrdinal] {
+        &(self.per_segment_new_term_ordinals[segment_ord])[..]
+    }
+
+    fn max_term_ord(&self) -> TermOrdinal {
+        self.per_segment_new_term_ordinals
+            .iter()
+            .flat_map(|term_ordinals| {
+                term_ordinals.iter().cloned().max()
+            })
+            .max()
+            .unwrap_or(TermOrdinal::default())
+    }
+}
+
 struct DeltaComputer {
     buffer: Vec<u32>,
 }
@@ -103,204 +145,384 @@ impl IndexMerger {
     }
 
     fn write_fieldnorms(&self, fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
-        let fieldnorm_fastfields: Vec<Field> = self.schema
-            .fields()
-            .iter()
-            .enumerate()
-            .filter(|&(_, field_entry)| field_entry.is_indexed())
-            .map(|(field_id, _)| Field(field_id as u32))
-            .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<()> {
-        let fast_fields: Vec<Field> = self.schema
-            .fields()
-            .iter()
-            .enumerate()
-            .filter(|&(_, field_entry)| field_entry.is_int_fast())
-            .map(|(field_id, _)| Field(field_id as u32))
-            .collect();
-        self.generic_write_fast_field(
-            fast_fields,
-            &extract_fast_field_reader,
-            fast_field_serializer,
-        )
-    }
-
-    // used both to merge field norms and regular u64 fast fields.
-    fn generic_write_fast_field(
-        &self,
-        fields: Vec<Field>,
-        field_reader_extractor: &Fn(&SegmentReader, Field) -> Option<FastFieldReader<u64>>,
-        fast_field_serializer: &mut FastFieldSerializer,
-    ) -> Result<()> {
-        for field in fields {
-            let mut u64_readers = vec![];
-            let mut min_val = u64::max_value();
-            let mut max_val = u64::min_value();
-
-            for reader in &self.readers {
-                match field_reader_extractor(reader, field) {
-                    Some(u64_reader) => {
-                        if let Some((seg_min_val, seg_max_val)) = compute_min_max_val(
-                            &u64_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);
-                            u64_readers.push((
-                                reader.max_doc(),
-                                u64_reader,
-                                reader.delete_bitset(),
-                            ));
-                        }
-                    }
-                    None => {
-                        let error_msg =
-                            format!("Failed to find a u64_reader for field {:?}", field);
-                        error!("{}", error_msg);
-                        bail!(ErrorKind::SchemaError(error_msg));
-                    }
+        for (field_id, field_entry) in self.schema.fields().iter().enumerate() {
+            let field = Field(field_id as u32);
+            if let FieldType::Str(ref text_options) = *field_entry.field_type() {
+                if text_options.get_indexing_options().is_some() {
+                    self.write_single_fast_field(
+                        field,
+                        &extract_fieldnorm_reader,
+                        fast_field_serializer,
+                    )?;
                 }
             }
-
-            if u64_readers.is_empty() {
-                // we have actually zero documents.
-                min_val = 0;
-                max_val = 0;
-            }
-
-            assert!(min_val <= max_val);
-
-            let mut fast_single_field_serializer =
-                fast_field_serializer.new_u64_fast_field(field, min_val, max_val)?;
-            for (max_doc, u64_reader, delete_bitset) in u64_readers {
-                for doc_id in 0..max_doc {
-                    if !delete_bitset.is_deleted(doc_id) {
-                        let val = u64_reader.get(doc_id);
-                        fast_single_field_serializer.add_val(val)?;
-                    }
-                }
-            }
-
-            fast_single_field_serializer.close_field()?;
         }
         Ok(())
     }
 
-    fn write_postings(&self, serializer: &mut InvertedIndexSerializer) -> Result<()> {
-        let mut delta_computer = DeltaComputer::new();
+    fn write_fast_fields(&self,
+                         fast_field_serializer: &mut FastFieldSerializer,
+                         mut term_ord_mappings: HashMap<Field, TermOrdinalMapping>) -> Result<()> {
+        for (field_id, field_entry) in self.schema.fields().iter().enumerate() {
+            let field = Field(field_id as u32);
+            let field_type = field_entry.field_type();
+            match *field_type {
+                FieldType::HierarchicalFacet => {
+                    let term_ordinal_mapping = term_ord_mappings
+                        .remove(&field)
+                        .expect("Logic Error in Tantivy (Please report). HierarchicalFact field should have required a\
+                        `term_ordinal_mapping`.");
+                    self.write_hierarchical_facet_field(
+                            field,
+                            term_ordinal_mapping,
+                            fast_field_serializer)?;
+                }
+                FieldType::U64(ref options) | FieldType::I64(ref options) => {
+                    match options.get_fastfield_cardinality() {
+                        Some(Cardinality::SingleValue) => {
+                            self.write_single_fast_field(
+                                field,
+                                &extract_fast_field_reader,
+                                fast_field_serializer
+                            )?;
+                        }
+                        Some(Cardinality::MultiValues) => {
+                            self.write_multi_fast_field(field, fast_field_serializer)?;
+                        }
+                        None => {}
+                    }
+                }
+                FieldType::Str(_) => {
+                    // We don't handle str fast field for the moment
+                    // They can be implemented using what is done
+                    // for facets in the future.
+                }
+            }
+        }
+        Ok(())
+    }
 
-        let mut indexed_fields = vec![];
-        for (field_ord, field_entry) in self.schema.fields().iter().enumerate() {
-            if field_entry.is_indexed() {
-                indexed_fields.push(Field(field_ord as u32));
+
+    // used both to merge field norms, `u64/i64` single fast fields.
+    fn write_single_fast_field(
+        &self,
+        field: Field,
+        field_reader_extractor: &Fn(&SegmentReader, Field) -> Option<FastFieldReader<u64>>,
+        fast_field_serializer: &mut FastFieldSerializer,
+    ) -> Result<()> {
+
+        let mut u64_readers = vec![];
+        let mut min_value = u64::max_value();
+        let mut max_value = u64::min_value();
+
+        for reader in &self.readers {
+            match field_reader_extractor(reader, field) {
+                Some(u64_reader) => {
+                    if let Some((seg_min_val, seg_max_val)) = compute_min_max_val(
+                        &u64_reader,
+                        reader.max_doc(),
+                        reader.delete_bitset(),
+                    ) {
+                        // the segment has some non-deleted documents
+                        min_value = cmp::min(min_value, seg_min_val);
+                        max_value = cmp::max(max_value, seg_max_val);
+                        u64_readers.push((
+                            reader.max_doc(),
+                            u64_reader,
+                             reader.delete_bitset(),
+                        ));
+                    } else {
+                        // all documents have been deleted.
+                    }
+                }
+                None => {
+                    let error_msg =
+                        format!("Failed to find a u64_reader for field {:?}", field);
+                    bail!(ErrorKind::SchemaError(error_msg));
+                }
+            }
+        }   
+
+        if min_value > max_value {
+            // There is not a single document remaining in the index.
+            min_value = 0;
+            max_value = 0;
+        }
+
+        let mut fast_single_field_serializer =
+            fast_field_serializer.new_u64_fast_field(field, min_value, max_value)?;
+        for (max_doc, u64_reader, delete_bitset) in u64_readers {
+            for doc_id in 0u32..max_doc {
+                if !delete_bitset.is_deleted(doc_id) {
+                    let val = u64_reader.get(doc_id);
+                    fast_single_field_serializer.add_val(val)?;
+                }
             }
         }
 
-        for indexed_field in indexed_fields {
-            let field_readers = self.readers
-                .iter()
-                .map(|reader| reader.inverted_index(indexed_field))
-                .collect::<Vec<_>>();
+        fast_single_field_serializer.close_field()?;
+        Ok(())
+    }
 
-            let field_term_streams = field_readers
-                .iter()
-                .map(|field_reader| field_reader.terms().stream())
-                .collect();
+    fn write_multi_fast_field_idx(&self,
+                                  field: Field,
+                                  fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
+        let mut total_num_vals = 0u64;
 
-            let mut merged_terms = TermMerger::new(field_term_streams);
-            let mut max_doc = 0;
-
-            // map from segment doc ids to the resulting merged segment doc id.
-            let mut merged_doc_id_map: Vec<Vec<Option<DocId>>> =
-                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;
+        // In the first pass, we compute the total number of vals.
+        //
+        // This is required by the bitpacker, as it needs to know
+        // what should be the bit length use for bitpacking.
+        for reader in &self.readers {
+            let multi_ff_reader = reader.multi_fast_field_reader::<u64>(field)?;
+            let delete_bitset = reader.delete_bitset();
+            if delete_bitset.has_deletes() {
+                for doc in 0u32..reader.max_doc() {
+                    if !delete_bitset.is_deleted(doc) {
+                        total_num_vals += multi_ff_reader.num_vals(doc) as u64;
                     }
                 }
-                merged_doc_id_map.push(segment_local_map);
+            } else {
+                total_num_vals += multi_ff_reader.total_num_vals();
             }
+        }
 
-            // Create the total list of doc ids
-            // by stacking the doc ids from the different segment.
-            //
-            // In the new segments, the doc id from the different
-            // segment are stacked so that :
-            // - Segment 0's doc ids become doc id [0, seg.max_doc]
-            // - Segment 1's doc ids become  [seg0.max_doc, seg0.max_doc + seg.max_doc]
-            // - Segment 2's doc ids become  [seg0.max_doc + seg1.max_doc,
-            //                                seg0.max_doc + seg1.max_doc + seg2.max_doc]
-            // ...
+        // We can now create our `idx` serializer, and in a second pass,
+        // can effectively push the different indexes.
+        let mut serialize_idx = fast_field_serializer.new_u64_fast_field_with_idx(field, 0, total_num_vals, 0)?;
+        let mut idx = 0;
+        for reader in &self.readers {
+            let multi_ff_reader = reader.multi_fast_field_reader::<u64>(field)?;
+            let delete_bitset = reader.delete_bitset();
+            for doc in 0u32..reader.max_doc() {
+                if !delete_bitset.is_deleted(doc) {
+                    serialize_idx.add_val(idx)?;
+                    idx += multi_ff_reader.num_vals(doc) as u64;
+                }
+            }
+        }
+        serialize_idx.add_val(idx)?;
+        serialize_idx.close_field()?;
+        Ok(())
+    }
 
-            let mut field_serializer = serializer.new_field(indexed_field)?;
+    fn write_hierarchical_facet_field(&self,
+                                      field: Field,
+                                      term_ordinal_mappings: TermOrdinalMapping,
+                                      fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
 
-            let field_entry = self.schema.get_field_entry(indexed_field);
+        // Multifastfield consists in 2 fastfields.
+        // The first serves as an index into the second one and is stricly increasing.
+        // The second contains the actual values.
 
-            // ... set segment postings option the new field.
-            let segment_postings_option =
-                field_entry.field_type().get_index_record_option().expect(
-                    "Encountered a field that is not supposed to be
-                         indexed. Have you modified the schema?",
-                );
+        // First we merge the idx fast field.
+        self.write_multi_fast_field_idx(field, fast_field_serializer)?;
 
-            while merged_terms.advance() {
-                let term_bytes: &[u8] = merged_terms.key();
-
-                // Let's compute the list of non-empty posting lists
-                let segment_postings: Vec<_> = merged_terms
-                    .current_kvs()
-                    .iter()
-                    .flat_map(|heap_item| {
-                        let segment_ord = heap_item.segment_ord;
-                        let term_info = heap_item.streamer.value();
-                        let segment_reader = &self.readers[heap_item.segment_ord];
-                        let inverted_index = segment_reader.inverted_index(indexed_field);
-                        let mut segment_postings = inverted_index
-                            .read_postings_from_terminfo(term_info, segment_postings_option);
-                        if segment_postings.advance() {
-                            Some((segment_ord, segment_postings))
-                        } else {
-                            None
+        // We can now write the actual fast field values.
+        // In the case of hierarchical facets, they are actually term ordinals.
+        let max_term_ord = term_ordinal_mappings.max_term_ord();
+        {
+            let mut serialize_vals = fast_field_serializer.new_u64_fast_field_with_idx(field, 0u64, max_term_ord, 1)?;
+            let mut vals = Vec::with_capacity(100);
+            for (segment_ord, segment_reader) in self.readers.iter().enumerate() {
+                let delete_bitset = segment_reader.delete_bitset();
+                let term_ordinal_mapping: &[TermOrdinal] = term_ordinal_mappings.get_segment(segment_ord);
+                let ff_reader: MultiValueIntFastFieldReader<u64> = segment_reader.multi_fast_field_reader(field)?;
+                // TODO optimize if no deletes
+                for doc in 0..segment_reader.max_doc() {
+                    if !delete_bitset.is_deleted(doc) {
+                        ff_reader.get_vals(doc, &mut vals);
+                        for &prev_term_ord in &vals {
+                            let new_term_ord = term_ordinal_mapping[prev_term_ord as usize];
+                            serialize_vals.add_val(new_term_ord)?;
                         }
-                    })
-                    .collect();
+                    }
+                }
+            }
+            serialize_vals.close_field()?;
+        }
+        Ok(())
+    }
 
-                // At this point, `segment_postings` contains the posting list
-                // of all of the segments containing the given term.
-                //
-                // These segments are non-empty and advance has already been called.
+    fn write_multi_fast_field(&self, field: Field, fast_field_serializer: &mut FastFieldSerializer) -> Result<()> {
 
-                if !segment_postings.is_empty() {
-                    // If not, the `term` will be entirely removed.
+        // Multifastfield consists in 2 fastfields.
+        // The first serves as an index into the second one and is stricly increasing.
+        // The second contains the actual values.
 
-                    // We know that there is at least one document containing
-                    // the term, so we add it.
-                    field_serializer.new_term(term_bytes)?;
+        // First we merge the idx fast field.
+        self.write_multi_fast_field_idx(field, fast_field_serializer)?;
 
-                    // 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];
-                        loop {
-                            // `.advance()` has been called once before the loop.
-                            // Hence we cannot use a `while segment_postings.advance()` loop.
-                            if let Some(remapped_doc_id) =
-                                old_to_new_doc_id[segment_postings.doc() as usize]
+        let mut min_value = u64::max_value();
+        let mut max_value = u64::min_value();
+
+        let mut vals = Vec::with_capacity(100);
+
+
+        // Our values are bitpacked and we need to know what should be
+        // our bitwidth and our minimum value before serializing any values.
+        //
+        // Computing those is non-trivial if some documents are deleted.
+        // We go through a complete first pass to compute the minimum and the
+        // maximum value and initialize our Serializer.
+        for reader in &self.readers {
+            let ff_reader: MultiValueIntFastFieldReader<u64> = reader.multi_fast_field_reader(field)?;
+            let delete_bitset = reader.delete_bitset();
+            for doc in 0u32..reader.max_doc() {
+                if !delete_bitset.is_deleted(doc) {
+                    ff_reader.get_vals(doc, &mut vals);
+                    for &val in &vals {
+                        min_value = cmp::min(val, min_value);
+                        max_value = cmp::max(val, max_value);
+                    }
+                }
+            }
+            // TODO optimize when no deletes
+        }
+
+        if min_value > max_value {
+            min_value = 0;
+            max_value = 0;
+        }
+
+        // We can now initialize our serializer, and push it the different values
+        {
+            let mut serialize_vals = fast_field_serializer.new_u64_fast_field_with_idx(field, min_value, max_value, 1)?;
+            for reader in &self.readers {
+                let delete_bitset = reader.delete_bitset();
+                let ff_reader: MultiValueIntFastFieldReader<u64> = reader.multi_fast_field_reader(field)?;
+                // TODO optimize if no deletes
+                for doc in 0..reader.max_doc() {
+                    if !delete_bitset.is_deleted(doc) {
+                        ff_reader.get_vals(doc, &mut vals);
+                        for &val in &vals {
+                            serialize_vals.add_val(val)?;
+                        }
+                    }
+                }
+            }
+            serialize_vals.close_field()?;
+        }
+        Ok(())
+    }
+
+    fn write_postings_for_field(&self,
+                                indexed_field: Field,
+                                field_type: &FieldType,
+                                serializer: &mut InvertedIndexSerializer) -> Result<Option<TermOrdinalMapping>> {
+        let mut delta_computer= DeltaComputer::new();
+        let field_readers = self.readers
+            .iter()
+            .map(|reader| reader.inverted_index(indexed_field))
+            .collect::<Vec<_>>();
+
+        let mut field_term_streams = Vec::new();
+        let mut max_term_ords: Vec<TermOrdinal> = Vec::new();
+
+        for field_reader in &field_readers {
+            let terms = field_reader.terms();
+            field_term_streams.push(terms.stream());
+            max_term_ords.push(terms.num_terms() as u64);
+        }
+
+        let mut term_ord_mapping_opt =
+            if *field_type == FieldType::HierarchicalFacet {
+                Some(TermOrdinalMapping::new(max_term_ords))
+            } else {
+                None
+            };
+
+
+        let mut merged_terms = TermMerger::new(field_term_streams);
+        let mut max_doc = 0;
+
+        // map from segment doc ids to the resulting merged segment doc id.
+        let mut merged_doc_id_map: Vec<Vec<Option<DocId>>> =
+            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);
+        }
+
+        // Create the total list of doc ids
+        // by stacking the doc ids from the different segment.
+        //
+        // In the new segments, the doc id from the different
+        // segment are stacked so that :
+        // - Segment 0's doc ids become doc id [0, seg.max_doc]
+        // - Segment 1's doc ids become  [seg0.max_doc, seg0.max_doc + seg.max_doc]
+        // - Segment 2's doc ids become  [seg0.max_doc + seg1.max_doc,
+        //                                seg0.max_doc + seg1.max_doc + seg2.max_doc]
+        // ...
+        let mut field_serializer = serializer.new_field(indexed_field)?;
+
+        let field_entry = self.schema.get_field_entry(indexed_field);
+
+        // ... set segment postings option the new field.
+        let segment_postings_option =
+            field_entry.field_type().get_index_record_option().expect(
+                "Encountered a field that is not supposed to be
+                         indexed. Have you modified the schema?",
+            );
+
+        while merged_terms.advance() {
+            let term_bytes: &[u8] = merged_terms.key();
+
+            // Let's compute the list of non-empty posting lists
+            let segment_postings: Vec<_> = merged_terms
+                .current_kvs()
+                .iter()
+                .flat_map(|heap_item| {
+                    let segment_ord = heap_item.segment_ord;
+                    let term_info = heap_item.streamer.value();
+                    let segment_reader = &self.readers[heap_item.segment_ord];
+                    let inverted_index = segment_reader.inverted_index(indexed_field);
+                    let mut segment_postings = inverted_index
+                        .read_postings_from_terminfo(term_info, segment_postings_option);
+                    if segment_postings.advance() {
+                        Some((segment_ord, segment_postings))
+                    } else {
+                        None
+                    }
+                })
+                .collect();
+
+            // At this point, `segment_postings` contains the posting list
+            // of all of the segments containing the given term.
+            //
+            // These segments are non-empty and advance has already been called.
+
+            if !segment_postings.is_empty() {
+                // If not, the `term` will be entirely removed.
+
+                // We know that there is at least one document containing
+                // the term, so we add it.
+                let to_term_ord = field_serializer.new_term(term_bytes)?;
+
+                if let Some(ref mut term_ord_mapping) = term_ord_mapping_opt {
+                    for (segment_ord, from_term_ord) in merged_terms.matching_segments() {
+                        term_ord_mapping.register_from_to(segment_ord,from_term_ord, to_term_ord);
+                    }
+                }
+
+                // 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];
+                    loop {
+                        // `.advance()` has been called once before the loop.
+                        // Hence we cannot use a `while segment_postings.advance()` loop.
+                        if let Some(remapped_doc_id) =
+                        old_to_new_doc_id[segment_postings.doc() as usize]
                             {
                                 // we make sure to only write the term iff
                                 // there is at least one document.
@@ -313,20 +535,31 @@ impl IndexMerger {
                                     delta_positions,
                                 )?;
                             }
-                            if !segment_postings.advance() {
-                                break;
-                            }
+                        if !segment_postings.advance() {
+                            break;
                         }
                     }
+                }
 
-                    // closing the term.
-                    field_serializer.close_term()?;
+                // closing the term.
+                field_serializer.close_term()?;
+            }
+        }
+        field_serializer.close()?;
+        Ok(term_ord_mapping_opt)
+    }
+
+    fn write_postings(&self, serializer: &mut InvertedIndexSerializer) -> Result<HashMap<Field, TermOrdinalMapping>> {
+        let mut term_ordinal_mappings = HashMap::new();
+        for (field_ord, field_entry) in self.schema.fields().iter().enumerate() {
+            if field_entry.is_indexed() {
+                let indexed_field = Field(field_ord as u32);
+                if let Some(term_ordinal_mapping) = self.write_postings_for_field(indexed_field, field_entry.field_type(), serializer)? {
+                    term_ordinal_mappings.insert(indexed_field, term_ordinal_mapping);
                 }
             }
-
-            field_serializer.close()?;
         }
-        Ok(())
+        Ok(term_ordinal_mappings)
     }
 
     fn write_storable_fields(&self, store_writer: &mut StoreWriter) -> Result<()> {
@@ -349,9 +582,9 @@ impl IndexMerger {
 
 impl SerializableSegment for IndexMerger {
     fn write(&self, mut serializer: SegmentSerializer) -> Result<u32> {
-        self.write_postings(serializer.get_postings_serializer())?;
+        let term_ord_mappings = self.write_postings(serializer.get_postings_serializer())?;
         self.write_fieldnorms(serializer.get_fieldnorms_serializer())?;
-        self.write_fast_fields(serializer.get_fast_field_serializer())?;
+        self.write_fast_fields(serializer.get_fast_field_serializer(), term_ord_mappings)?;
         self.write_storable_fields(serializer.get_store_writer())?;
         serializer.close()?;
         Ok(self.max_doc)
@@ -375,6 +608,10 @@ mod tests {
     use schema::IndexRecordOption;
     use schema::Cardinality;
     use futures::Future;
+    use IndexWriter;
+    use query::AllQuery;
+    use collector::FacetCollector;
+    use schema::IntOptions;
 
     #[test]
     fn test_index_merger_no_deletes() {
@@ -805,4 +1042,297 @@ mod tests {
             assert_eq!(searcher.num_docs(), 0);
         }
     }
+
+
+    #[test]
+    fn test_merge_facets() {
+        let mut schema_builder = schema::SchemaBuilder::default();
+        let facet_field = schema_builder.add_facet_field("facet");
+        let index = Index::create_in_ram(schema_builder.build());
+        use schema::Facet;
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            let index_doc = |index_writer: &mut IndexWriter, doc_facets: &[&str]| {
+                let mut doc = Document::default();
+                for facet in doc_facets {
+                    doc.add_facet(facet_field, Facet::from(facet));
+                }
+                index_writer.add_document(doc);
+            };
+
+            index_doc(&mut index_writer, &["/top/a/firstdoc", "/top/b"]);
+            index_doc(&mut index_writer, &["/top/a/firstdoc", "/top/b", "/top/c"]);
+            index_doc(&mut index_writer, &["/top/a", "/top/b"]);
+            index_doc(&mut index_writer, &["/top/a"]);
+
+            index_doc(&mut index_writer, &["/top/b", "/top/d"]);
+            index_doc(&mut index_writer, &["/top/d"]);
+            index_doc(&mut index_writer, &["/top/e"]);
+            index_writer.commit().expect("committed");
+
+            index_doc(&mut index_writer, &["/top/a"]);
+            index_doc(&mut index_writer, &["/top/b"]);
+            index_doc(&mut index_writer, &["/top/c"]);
+            index_writer.commit().expect("committed");
+
+            index_doc(&mut index_writer, &["/top/e", "/top/f"]);
+            index_writer.commit().expect("committed");
+        }
+        index.load_searchers().unwrap();
+        let test_searcher = |expected_num_docs: usize, expected: &[(&str, u64)]| {
+            let searcher = index.searcher();
+            let mut facet_collector = FacetCollector::for_field(facet_field);
+            facet_collector.add_facet(Facet::from("/top"));
+            use collector::{MultiCollector, CountCollector};
+            let mut count_collector = CountCollector::default();
+            {
+                let mut multi_collectors = MultiCollector::from(vec![&mut count_collector, &mut facet_collector]);
+                searcher.search(&AllQuery, &mut multi_collectors).unwrap();
+            }
+            assert_eq!(count_collector.count(), expected_num_docs);
+            let facet_counts = facet_collector.harvest();
+            let facets: Vec<(String, u64)> = facet_counts.get("/top")
+                .map(|(facet, count)| (facet.to_string(), count))
+                .collect();
+            assert_eq!(
+                facets,
+                expected
+                    .iter()
+                    .map(|&(facet_str, count)| (String::from(facet_str), count))
+                    .collect::<Vec<_>>()
+            );
+        };
+        test_searcher(11, &[
+            ("/top/a", 5),
+            ("/top/b", 5),
+            ("/top/c", 2),
+            ("/top/d", 2),
+            ("/top/e", 2),
+            ("/top/f", 1)
+        ]);
+
+        // Merging the 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(&segment_ids)
+                .wait()
+                .expect("Merging failed");
+            index_writer.wait_merging_threads().unwrap();
+
+            index.load_searchers().unwrap();
+            test_searcher(11, &[
+                ("/top/a", 5),
+                ("/top/b", 5),
+                ("/top/c", 2),
+                ("/top/d", 2),
+                ("/top/e", 2),
+                ("/top/f", 1)
+            ]);
+        }
+
+        // Deleting one term
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            let facet = Facet::from_path(vec!["top", "a", "firstdoc"]);
+            let facet_term = Term::from_facet(facet_field, &facet);
+            index_writer.delete_term(facet_term);
+            index_writer.commit().unwrap();
+            index.load_searchers().unwrap();
+            test_searcher(9, &[
+                ("/top/a", 3),
+                ("/top/b", 3),
+                ("/top/c", 1),
+                ("/top/d", 2),
+                ("/top/e", 2),
+                ("/top/f", 1)
+            ]);
+        }
+
+    }
+
+
+    #[test]
+    fn test_merge_multivalued_int_fields_all_deleted() {
+        let mut schema_builder = schema::SchemaBuilder::default();
+        let int_options = IntOptions::default()
+            .set_fast(Cardinality::MultiValues)
+            .set_indexed();
+        let int_field = schema_builder.add_u64_field("intvals", int_options);
+        let index = Index::create_in_ram(schema_builder.build());
+
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            let mut doc = Document::default();
+            doc.add_u64(int_field,  1);
+            index_writer.add_document(doc.clone());
+            index_writer.commit().expect("commit failed");
+            index_writer.add_document(doc);
+            index_writer.commit().expect("commit failed");
+            index_writer.delete_term(Term::from_field_u64(int_field, 1));
+            index_writer.commit().expect("commit failed");
+        }
+        index.load_searchers().unwrap();
+        let searcher = index.searcher();
+        assert_eq!(searcher.num_docs(), 0);
+        // Merging the 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(&segment_ids)
+                .wait()
+                .expect("Merging failed");
+            index_writer.wait_merging_threads().unwrap();
+        }
+        index.load_searchers().unwrap();
+        let searcher = index.searcher();
+        assert_eq!(searcher.num_docs(), 0);
+    }
+
+    #[test]
+    fn test_merge_multivalued_int_fields() {
+        let mut schema_builder = schema::SchemaBuilder::default();
+        let int_options = IntOptions::default()
+            .set_fast(Cardinality::MultiValues)
+            .set_indexed();
+        let int_field = schema_builder.add_u64_field("intvals", int_options);
+        let index = Index::create_in_ram(schema_builder.build());
+
+
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 40_000_000).unwrap();
+            let index_doc = |index_writer: &mut IndexWriter, int_vals: &[u64]| {
+                let mut doc = Document::default();
+                for &val in int_vals {
+                    doc.add_u64(int_field,  val);
+                }
+                index_writer.add_document(doc);
+            };
+
+            index_doc(&mut index_writer, &[1, 2]);
+            index_doc(&mut index_writer, &[1, 2, 3]);
+            index_doc(&mut index_writer, &[4, 5]);
+            index_doc(&mut index_writer, &[1, 2]);
+            index_doc(&mut index_writer, &[1, 5]);
+            index_doc(&mut index_writer, &[3]);
+            index_doc(&mut index_writer, &[17]);
+            index_writer.commit().expect("committed");
+
+            index_doc(&mut index_writer, &[20]);
+            index_writer.commit().expect("committed");
+
+            index_doc(&mut index_writer, &[28, 27]);
+            index_doc(&mut index_writer, &[1_000]);
+
+            index_writer.commit().expect("committed");
+        }
+        index.load_searchers().unwrap();
+
+        let searcher = index.searcher();
+
+        let mut vals: Vec<u64> = Vec::new();
+
+        {
+            let segment = searcher.segment_reader(0u32);
+            let ff_reader = segment.multi_fast_field_reader(int_field).unwrap();
+
+            ff_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[1, 2]);
+
+            ff_reader.get_vals(1, &mut vals);
+            assert_eq!(&vals, &[1, 2, 3]);
+
+            ff_reader.get_vals(2, &mut vals);
+            assert_eq!(&vals, &[4, 5]);
+
+            ff_reader.get_vals(3, &mut vals);
+            assert_eq!(&vals, &[1, 2]);
+
+            ff_reader.get_vals(4, &mut vals);
+            assert_eq!(&vals, &[1, 5]);
+
+            ff_reader.get_vals(5, &mut vals);
+            assert_eq!(&vals, &[3]);
+
+            ff_reader.get_vals(6, &mut vals);
+            assert_eq!(&vals, &[17]);
+        }
+
+
+        {
+            let segment = searcher.segment_reader(1u32);
+            let ff_reader = segment.multi_fast_field_reader(int_field).unwrap();
+            ff_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[20]);
+        }
+
+        {
+            let segment = searcher.segment_reader(2u32);
+            let ff_reader = segment.multi_fast_field_reader(int_field).unwrap();
+            ff_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[28, 27]);
+
+            ff_reader.get_vals(1, &mut vals);
+            assert_eq!(&vals, &[1_000]);
+        }
+
+        // Merging the 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(&segment_ids)
+                .wait()
+                .expect("Merging failed");
+            index_writer.wait_merging_threads().unwrap();
+        }
+
+        index.load_searchers().unwrap();
+
+        {
+            let searcher = index.searcher();
+            let segment = searcher.segment_reader(0u32);
+            let ff_reader = segment.multi_fast_field_reader(int_field).unwrap();
+
+            ff_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[1, 2]);
+
+            ff_reader.get_vals(1, &mut vals);
+            assert_eq!(&vals, &[1, 2, 3]);
+
+            ff_reader.get_vals(2, &mut vals);
+            assert_eq!(&vals, &[4, 5]);
+
+            ff_reader.get_vals(3, &mut vals);
+            assert_eq!(&vals, &[1, 2]);
+
+            ff_reader.get_vals(4, &mut vals);
+            assert_eq!(&vals, &[1, 5]);
+
+            ff_reader.get_vals(5, &mut vals);
+            assert_eq!(&vals, &[3]);
+
+            ff_reader.get_vals(6, &mut vals);
+            assert_eq!(&vals, &[17]);
+
+            ff_reader.get_vals(7, &mut vals);
+            assert_eq!(&vals, &[20]);
+
+            ff_reader.get_vals(8, &mut vals);
+            assert_eq!(&vals, &[28, 27]);
+
+            ff_reader.get_vals(9, &mut vals);
+            assert_eq!(&vals, &[1_000]);
+        }
+
+    }
 }
+

src/postings/postings_writer.rs

@@ -16,6 +16,7 @@ use tokenizer::Token;
 use tokenizer::TokenStream;
 use schema::IndexRecordOption;
 use postings::UnorderedTermId;
+use termdict::TermOrdinal;
 
 fn posting_from_field_entry<'a>(
     field_entry: &FieldEntry,
@@ -44,6 +45,7 @@ fn posting_from_field_entry<'a>(
 
 pub struct MultiFieldPostingsWriter<'a> {
     heap: &'a Heap,
+    schema: Schema,
     term_index: TermHashMap<'a>,
     per_field_postings_writers: Vec<Box<PostingsWriter + 'a>>,
 }
@@ -58,8 +60,8 @@ impl<'a> MultiFieldPostingsWriter<'a> {
             .iter()
             .map(|field_entry| posting_from_field_entry(field_entry, heap))
             .collect();
-
         MultiFieldPostingsWriter {
+            schema: schema.clone(),
             heap,
             term_index,
             per_field_postings_writers,
@@ -83,7 +85,7 @@ impl<'a> MultiFieldPostingsWriter<'a> {
     pub fn serialize(
         &self,
         serializer: &mut InvertedIndexSerializer,
-    ) -> Result<HashMap<Field, HashMap<UnorderedTermId, usize>>> {
+    ) -> Result<HashMap<Field, HashMap<UnorderedTermId, TermOrdinal>>> {
         let mut term_offsets: Vec<(&[u8], u32, UnorderedTermId)> = self.term_index.iter().collect();
         term_offsets.sort_by_key(|&(k, _, _)| k);
 
@@ -94,7 +96,7 @@ impl<'a> MultiFieldPostingsWriter<'a> {
             .map(|(key, _, _)| Term::wrap(key).field())
             .enumerate();
 
-        let mut unordered_term_mappings: HashMap<Field, HashMap<UnorderedTermId, usize>> =
+        let mut unordered_term_mappings: HashMap<Field, HashMap<UnorderedTermId, TermOrdinal>> =
             HashMap::new();
 
         let mut prev_field = Field(u32::max_value());
@@ -110,17 +112,23 @@ impl<'a> MultiFieldPostingsWriter<'a> {
             let (field, start) = offsets[i];
             let (_, stop) = offsets[i + 1];
 
-            // populating the unordered term ord -> ordered term ord mapping
-            // for the field.
-            let mut mapping = HashMap::new();
-            for (term_ord, term_unord_id) in term_offsets[start..stop]
-                .iter()
-                .map(|&(_, _, bucket)| bucket)
-                .enumerate()
-            {
-                mapping.insert(term_unord_id, term_ord);
+            let field_entry = self.schema.get_field_entry(field);
+
+            match field_entry.field_type() {
+                FieldType::Str(_) | FieldType::HierarchicalFacet => {
+                    // populating the (unordered term ord) -> (ordered term ord) mapping
+                    // for the field.
+                    let mut unordered_term_ids = term_offsets[start..stop]
+                        .iter()
+                        .map(|&(_, _, bucket)| bucket);
+                    let mut mapping: HashMap<UnorderedTermId, TermOrdinal> = unordered_term_ids
+                        .enumerate()
+                        .map(|(term_ord, unord_term_id)| (unord_term_id as UnorderedTermId, term_ord as TermOrdinal))
+                        .collect();
+                    unordered_term_mappings.insert(field, mapping);
+                }
+                FieldType::U64(_) | FieldType::I64(_) => {}
             }
-            unordered_term_mappings.insert(field, mapping);
 
             let postings_writer = &self.per_field_postings_writers[field.0 as usize];
             let mut field_serializer = serializer.new_field(field)?;

src/postings/serializer.rs

@@ -13,7 +13,7 @@ use std::io::{self, Write};
 use compression::VIntEncoder;
 use common::CountingWriter;
 use common::CompositeWrite;
-use termdict::TermDictionaryBuilder;
+use termdict::{TermOrdinal, TermDictionaryBuilder};
 
 /// `PostingsSerializer` is in charge of serializing
 /// postings on disk, in the
@@ -114,6 +114,7 @@ pub struct FieldSerializer<'a> {
     positions_serializer_opt: Option<PositionSerializer<&'a mut CountingWriter<WritePtr>>>,
     current_term_info: TermInfo,
     term_open: bool,
+    num_terms: TermOrdinal,
 }
 
 impl<'a> FieldSerializer<'a> {
@@ -152,6 +153,7 @@ impl<'a> FieldSerializer<'a> {
             positions_serializer_opt,
             current_term_info: TermInfo::default(),
             term_open: false,
+            num_terms: TermOrdinal::default(),
         })
     }
 
@@ -172,7 +174,7 @@ impl<'a> FieldSerializer<'a> {
     /// * 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: &[u8]) -> io::Result<()> {
+    pub fn new_term(&mut self, term: &[u8]) -> io::Result<TermOrdinal> {
         assert!(
             !self.term_open,
             "Called new_term, while the previous term was not closed."
@@ -180,7 +182,10 @@ impl<'a> FieldSerializer<'a> {
         self.term_open = true;
         self.postings_serializer.clear();
         self.current_term_info = self.current_term_info();
-        self.term_dictionary_builder.insert_key(term)
+        self.term_dictionary_builder.insert_key(term)?;
+        let term_ordinal = self.num_terms;
+        self.num_terms += 1;
+        Ok(term_ordinal)
     }
 
     /// Serialize the information that a document contains the current term,

src/query/all_query.rs

@@ -7,6 +7,7 @@ use Result;
 use Score;
 use DocId;
 use core::Searcher;
+use fastfield::DeleteBitSet;
 
 /// Query that matches all of the documents.
 ///
@@ -26,28 +27,52 @@ pub struct AllWeight;
 impl Weight for AllWeight {
     fn scorer(&self, reader: &SegmentReader) -> Result<Box<Scorer>> {
         Ok(box AllScorer {
-            started: false,
+            state: State::NotStarted,
             doc: 0u32,
             max_doc: reader.max_doc(),
+            deleted_bitset: reader.delete_bitset().clone()
         })
     }
 }
 
+enum State {
+    NotStarted,
+    Started,
+    Finished
+}
+
 /// Scorer associated to the `AllQuery` query.
 pub struct AllScorer {
-    started: bool,
+    state: State,
     doc: DocId,
     max_doc: DocId,
+    deleted_bitset: DeleteBitSet
 }
 
 impl DocSet for AllScorer {
     fn advance(&mut self) -> bool {
-        if self.started {
-            self.doc += 1u32;
-        } else {
-            self.started = true;
+        loop {
+            match self.state {
+                State::NotStarted => {
+                    self.state = State::Started;
+                    self.doc = 0;
+                }
+                State::Started => {
+                    self.doc += 1u32;
+                }
+                State::Finished => {
+                    return false;
+                }
+            }
+            if self.doc < self.max_doc {
+                if !self.deleted_bitset.is_deleted(self.doc) {
+                    return true;
+                }
+            } else {
+                self.state = State::Finished;
+                return false;
+            }
         }
-        self.doc < self.max_doc
     }
 
     fn doc(&self) -> DocId {

src/schema/facet.rs

@@ -212,6 +212,14 @@ mod tests {
         assert!(Facet::root().is_root());
     }
 
+    #[test]
+    fn test_from_path() {
+        assert_eq!(
+            Facet::from_path(vec!["top", "a", "firstdoc"]),
+            Facet::from("/top/a/firstdoc")
+        );
+    }
+
     #[test]
     fn test_facet_display() {
         {

src/schema/term.rs

@@ -4,6 +4,7 @@ use common;
 use byteorder::{BigEndian, ByteOrder};
 use super::Field;
 use std::str;
+use schema::Facet;
 
 /// Size (in bytes) of the buffer of a int field.
 const INT_TERM_LEN: usize = 4 + 8;
@@ -29,6 +30,16 @@ impl Term {
         Term::from_field_u64(field, val_u64)
     }
 
+    /// Creates a `Term` given a facet.
+    pub fn from_facet(field: Field, facet: &Facet) -> Term {
+        let bytes = facet.encoded_bytes();
+        let buffer = Vec::with_capacity(4 + bytes.len());
+        let mut term = Term(buffer);
+        term.set_field(field);
+        term.set_bytes(bytes);
+        term
+    }
+
     /// Builds a term given a field, and a string value
     ///
     /// Assuming the term has a field id of 2, and a text value of "abc",
@@ -91,10 +102,14 @@ impl Term {
         self.set_u64(common::i64_to_u64(val));
     }
 
+    fn set_bytes(&mut self, bytes: &[u8]) {
+        self.0.resize(4, 0u8);
+        self.0.extend(bytes);
+    }
+
     /// Set the texts only, keeping the field untouched.
     pub fn set_text(&mut self, text: &str) {
-        self.0.resize(4, 0u8);
-        self.0.extend(text.as_bytes());
+        self.set_bytes(text.as_bytes());
     }
 }
 

src/termdict/fstdict/streamer.rs

@@ -86,4 +86,8 @@ impl<'a> TermStreamer for TermStreamerImpl<'a> {
     fn value(&self) -> &TermInfo {
         &self.current_value
     }
+
+    fn max_term_ord(&self) -> TermOrdinal {
+        self.fst_map.num_terms() as TermOrdinal
+    }
 }

src/termdict/merger.rs

@@ -2,6 +2,7 @@ use std::collections::BinaryHeap;
 use termdict::TermStreamerImpl;
 use std::cmp::Ordering;
 use termdict::TermStreamer;
+use termdict::TermOrdinal;
 use schema::Term;
 
 pub struct HeapItem<'a> {
@@ -29,6 +30,7 @@ impl<'a> Ord for HeapItem<'a> {
     }
 }
 
+
 /// Given a list of sorted term streams,
 /// returns an iterator over sorted unique terms.
 ///
@@ -43,8 +45,6 @@ pub struct TermMerger<'a> {
 
 impl<'a> TermMerger<'a> {
     /// Stream of merged term dictionary
-    ///
-    ///
     pub fn new(streams: Vec<TermStreamerImpl<'a>>) -> TermMerger<'a> {
         TermMerger {
             heap: BinaryHeap::new(),
@@ -59,6 +59,14 @@ impl<'a> TermMerger<'a> {
         }
     }
 
+    pub(crate) fn matching_segments<'b: 'a>(&'b self) -> Box<'b + Iterator<Item=(usize, TermOrdinal)>> {
+        Box::new(self.current_streamers
+            .iter()
+            .map(|heap_item| {
+                (heap_item.segment_ord, heap_item.streamer.term_ord())
+            }))
+    }
+
     fn advance_segments(&mut self) {
         let streamers = &mut self.current_streamers;
         let heap = &mut self.heap;

src/termdict/mod.rs

@@ -197,6 +197,13 @@ pub trait TermStreamer: Sized {
             None
         }
     }
+
+
+    /// Returns an upperbound for term ordinals in this stream.
+    ///
+    /// All term ordinals are guaranteed to be stricly smaller
+    /// than the result of `.max_term_ord()`
+    fn max_term_ord(&self) -> TermOrdinal;
 }
 
 /// `TermStreamerBuilder` is an helper object used to define

src/tokenizer/tokenizer.rs

@@ -6,21 +6,21 @@ use tokenizer::TokenStreamChain;
 
 /// Token
 pub struct Token {
-    /// Offset (byte index) of the first character of the token.
-    /// Offsets shall not be modified by token filters.
-    pub offset_from: usize,
-    /// Offset (byte index) of the last character of the token + 1.
-    /// The text that generated the token should be obtained by
-    /// &text[token.offset_from..token.offset_to]
-    pub offset_to: usize,
-    /// Position, expressed in number of tokens.
-    pub position: usize,
-    /// Actual text content of the token.
-    pub text: String,
+        /// Offset (byte index) of the first character of the token.
+        /// Offsets shall not be modified by token filters.
+        pub offset_from: usize,
+        /// Offset (byte index) of the last character of the token + 1.
+        /// The text that generated the token should be obtained by
+        /// &text[token.offset_from..token.offset_to]
+        pub offset_to: usize,
+        /// Position, expressed in number of tokens.
+        pub position: usize,
+        /// Actual text content of the token.
+        pub text: String,
 }
 
 impl Default for Token {
-    fn default() -> Token {
+    fn default() -> Token           {
         Token {
             offset_from: 0,
             offset_to: 0,