NOBUG Added setting merge policy.

src/indexer/index_writer.rs

@@ -5,6 +5,7 @@ use core::SerializableSegment;
 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;
@@ -15,6 +16,7 @@ use indexer::merger::IndexMerger;
 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};
@@ -53,6 +55,8 @@ pub struct IndexWriter {
     // lifetime of the lock with that of the IndexWriter.
     _directory_lock: DirectoryLock, 
     
+    _merge_policy: Arc<Mutex<Box<MergePolicy>>>,
+    
     index: Index,
     heap_size_in_bytes_per_thread: usize,
 
@@ -204,12 +208,16 @@ impl IndexWriter {
         let (document_sender, document_receiver): (DocumentSender, DocumentReceiver) =
             chan::sync(PIPELINE_MAX_SIZE_IN_DOCS);
         
-        let (segment_update_sender, segment_update_thread) = SegmentUpdater::start_updater(index.clone());
+        let merge_policy: Arc<Mutex<Box<MergePolicy>>> = 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(),
 
@@ -229,7 +237,18 @@ impl IndexWriter {
         try!(index_writer.start_workers());
         Ok(index_writer)
     }
-
+    
+    
+    /// Returns a clone of the index_writer merge policy.
+    pub fn get_merge_policy(&self) -> Box<MergePolicy> {
+        self._merge_policy.lock().unwrap().box_clone() 
+    }
+    
+    /// Set the merge policy.
+    pub fn set_merge_policy(&self, merge_policy: Box<MergePolicy>) {
+        *self._merge_policy.lock().unwrap() = merge_policy;
+    }
+    
     fn start_workers(&mut self) -> Result<()> {
         for _ in 0..self.num_threads {
             try!(self.add_indexing_worker());
@@ -445,6 +464,7 @@ mod tests {
     use Index;
     use Term;
     use Error;
+    use indexer::NoMergePolicy;
 
     #[test]
     fn test_lockfile_stops_duplicates() {
@@ -456,6 +476,17 @@ mod tests {
             _ => panic!("Expected FileAlreadyExists error"),
         }
     }
+    
+    #[test]
+    fn test_set_merge_policy() {
+        let schema_builder = schema::SchemaBuilder::default();
+        let index = Index::create_in_ram(schema_builder.build());
+        let index_writer = index.writer(40_000_000).unwrap();
+        assert_eq!(format!("{:?}", index_writer.get_merge_policy()), "LogMergePolicy { min_merge_size: 8, min_layer_size: 10000, level_log_size: 0.75 }");
+        let merge_policy = box NoMergePolicy::default();
+        index_writer.set_merge_policy(merge_policy);
+        assert_eq!(format!("{:?}", index_writer.get_merge_policy()), "NoMergePolicy");
+    }
 
     #[test]
     fn test_lockfile_released_on_drop() {

src/indexer/log_merge_policy.rs

@@ -8,6 +8,10 @@ const DEFAULT_LEVEL_LOG_SIZE: f64 = 0.75;
 const DEFAULT_MIN_LAYER_SIZE: u32 = 10_000;
 const DEFAULT_MIN_MERGE_SIZE: usize = 8;
 
+
+/// LogMergePolicy tries tries to merge segments that have a similar number of 
+/// documents.
+#[derive(Debug, Clone)]
 pub struct LogMergePolicy {
     min_merge_size: usize,
     min_layer_size: u32,
@@ -20,7 +24,7 @@ impl LogMergePolicy {
     }
 
     /// Set the minimum number of segment that may be merge together.
-    pub fn set_min_merge_size(&mut self, min_merge_size: usize) {
+        pub fn set_min_merge_size(&mut self, min_merge_size: usize) {
         self.min_merge_size = min_merge_size;
     }
 
@@ -30,7 +34,6 @@ impl LogMergePolicy {
         self.min_layer_size = min_layer_size;
     }
 
-
     /// Set the ratio between two consecutive levels.
     ///
     /// Segment are group in levels according to their sizes.
@@ -83,6 +86,10 @@ impl MergePolicy for LogMergePolicy {
 
         result
     }
+    
+    fn box_clone(&self) -> Box<MergePolicy> {
+        box self.clone()
+    }
 }
 
 impl Default for LogMergePolicy {

src/indexer/merge_policy.rs

@@ -1,15 +1,30 @@
 use core::SegmentId;
 use core::SegmentMeta;
 use std::marker;
+use std::fmt::Debug;
 
 
+/// Set of segment suggested for a merge. 
 #[derive(Debug, Clone)]
 pub struct MergeCandidate(pub Vec<SegmentId>);
 
-pub trait MergePolicy: marker::Send {
+
+/// The Merge policy defines which segments should be merged. 
+/// 
+/// 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 {
+    /// Given the list of segment metas, returns the list of merge candidates. 
+    ///
+    /// This call happens on the segment updater thread, and will block 
+    /// other segment updates, so all implementations should happen rapidly. 
     fn compute_merge_candidates(&self, segments: &[SegmentMeta]) -> Vec<MergeCandidate>;
+    /// Returns a boxed clone of the MergePolicy.
+    fn box_clone(&self) -> Box<MergePolicy>;
 }
 
+/// Never merge segments. 
+#[derive(Debug)]
 pub struct NoMergePolicy;
 
 impl Default for NoMergePolicy {
@@ -18,10 +33,13 @@ impl Default for NoMergePolicy {
     }
 }
 
-
 impl MergePolicy for NoMergePolicy {
     fn compute_merge_candidates(&self, _segments: &[SegmentMeta]) -> Vec<MergeCandidate> {
         Vec::new()
     }
+    
+    fn box_clone(&self) -> Box<MergePolicy> {
+        box NoMergePolicy
+    }
 }
 

src/indexer/mod.rs

@@ -17,4 +17,6 @@ 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;

src/indexer/segment_updater.rs

@@ -2,12 +2,13 @@
 
 use chan;
 use core::Index;
+use std::sync::Mutex;
 use core::Segment;
 use core::SegmentId;
 use core::SegmentMeta;
 use std::mem;
 use core::SerializableSegment;
-use indexer::{DefaultMergePolicy, MergePolicy};
+use indexer::MergePolicy;
 use indexer::MergeCandidate;
 use indexer::merger::IndexMerger;
 use indexer::SegmentSerializer;
@@ -135,7 +136,7 @@ pub struct SegmentUpdater {
 	segment_update_receiver: SegmentUpdateReceiver,
 	segment_update_sender: SegmentUpdateSender,
     segment_manager_arc: Arc<SegmentManager>,
-    merge_policy: Box<MergePolicy>,
+    merge_policy: Arc<Mutex<Box<MergePolicy>>>,
     merging_thread_id: usize,
     merging_threads: HashMap<usize, JoinHandle<(Vec<SegmentId>, SegmentMeta)> >, 
 }
@@ -143,12 +144,12 @@ pub struct SegmentUpdater {
 
 impl SegmentUpdater {
 	    
-    pub fn start_updater(index: Index) -> (SegmentUpdateSender, JoinHandle<()>) {
-        let segment_updater = SegmentUpdater::new(index);
+    pub fn start_updater(index: Index, merge_policy: Arc<Mutex<Box<MergePolicy>>>) -> (SegmentUpdateSender, JoinHandle<()>) {
+        let segment_updater = SegmentUpdater::new(index, merge_policy);
         (segment_updater.segment_update_sender.clone(), segment_updater.start())
     }
     
-    fn new(index: Index) -> SegmentUpdater {
+    fn new(index: Index, merge_policy: Arc<Mutex<Box<MergePolicy>>>) -> SegmentUpdater {
         let segment_manager_arc = get_segment_manager(&index);
         let (segment_update_sender, segment_update_receiver): (SegmentUpdateSender, SegmentUpdateReceiver) = chan::async();
 		SegmentUpdater {
@@ -157,7 +158,7 @@ impl SegmentUpdater {
             segment_update_sender: segment_update_sender,
             segment_update_receiver: segment_update_receiver,
             segment_manager_arc: segment_manager_arc,
-            merge_policy: Box::new(DefaultMergePolicy::default()), // TODO make that configurable
+            merge_policy: merge_policy,
             merging_thread_id: 0,
             merging_threads: HashMap::new(), 
 		}
@@ -236,8 +237,9 @@ impl SegmentUpdater {
         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 mut merge_candidates = self.merge_policy.compute_merge_candidates(&uncommitted_segments);
-        let committed_merge_candidates = self.merge_policy.compute_merge_candidates(&committed_segments);
+        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
     }

src/lib.rs

@@ -112,6 +112,16 @@ pub use postings::Postings;
 pub use postings::SegmentPostingsOption;
 
 
+
+/// Tantivy's makes it possible to personalize when 
+/// the indexer should merge its segments
+pub mod merge_policy {
+    pub use indexer::MergePolicy;
+    pub use indexer::LogMergePolicy;
+    pub use indexer::NoMergePolicy;
+    pub use indexer::DefaultMergePolicy;
+}
+
 /// u32 identifying a document within a segment.
 /// Documents have their doc id assigned incrementally,
 /// as they are added in the segment.