Collector refactoring and multithreaded search (#437)

* Split Collector into an overall Collector and a per-segment SegmentCollector. Precursor to cross-segment parallelism, and as a side benefit cleans up any per-segment fields from being Option<T> to just T.

* Attempt to add MultiCollector back

* working. Chained collector is broken though

* Fix chained collector

* Fix test

* Make Weight Send+Sync for parallelization purposes

* Expose parameters of RangeQuery for external usage

* Removed &mut self

* fixing tests

* Restored TestCollectors

* blop

* multicollector working

* chained collector working

* test broken

* fixing unit test

* blop

* blop

* Blop

* simplifying APi

* blop

* better syntax

* Simplifying top_collector

* refactoring

* blop

* Sync with master

* Added multithread search

* Collector refactoring

* Schema::builder

* CR and rustdoc

* CR comments

* blop

* Added an executor

* Sorted the segment readers in the searcher

* Update searcher.rs

* Fixed unit testst

* changed the place where we have the sort-segment-by-count heuristic

* using crossbeam::channel

* inlining

* Comments about panics propagating

* Added unit test for executor panicking

* Readded default

* Removed Default impl

* Added unit test for executor

1 files changed, 7 insertions, 18 deletions

diff --git a/src/query/scorer.rs b/src/query/scorer.rs
index 2c2f0cd..a2e40fa 100644
--- a/src/query/scorer.rs
+++ b/src/query/scorer.rs
@@ -1,8 +1,6 @@
-use collector::Collector;
 use common::BitSet;
 use docset::{DocSet, SkipResult};
 use downcast;
-use fastfield::DeleteBitSet;
 use std::ops::DerefMut;
 use DocId;
 use Score;
@@ -16,20 +14,11 @@ pub trait Scorer: downcast::Any + DocSet + 'static {
     /// This method will perform a bit of computation and is not cached.
     fn score(&mut self) -> Score;
 
-    /// Consumes the complete `DocSet` and
-    /// push the scored documents to the collector.
-    fn collect(&mut self, collector: &mut Collector, delete_bitset_opt: Option<&DeleteBitSet>) {
-        if let Some(delete_bitset) = delete_bitset_opt {
-            while self.advance() {
-                let doc = self.doc();
-                if !delete_bitset.is_deleted(doc) {
-                    collector.collect(doc, self.score());
-                }
-            }
-        } else {
-            while self.advance() {
-                collector.collect(self.doc(), self.score());
-            }
+    /// Iterates through all of the document matched by the DocSet
+    /// `DocSet` and push the scored documents to the collector.
+    fn for_each(&mut self, callback: &mut FnMut(DocId, Score)) {
+        while self.advance() {
+            callback(self.doc(), self.score());
         }
     }
 }
@@ -44,9 +33,9 @@ impl Scorer for Box<Scorer> {
         self.deref_mut().score()
     }
 
-    fn collect(&mut self, collector: &mut Collector, delete_bitset: Option<&DeleteBitSet>) {
+    fn for_each(&mut self, callback: &mut FnMut(DocId, Score)) {
         let scorer = self.deref_mut();
-        scorer.collect(collector, delete_bitset);
+        scorer.for_each(callback);
     }
 }