Search: Reuse Lucene's MultiCollector.

We could reuse Lucene's MultiCollector instead of implementing our own.

Close #9549

src/main/java/org/elasticsearch/common/lucene/MultiCollector.java

@@ -1,85 +0,0 @@
-/*
- * Licensed to Elasticsearch under one or more contributor
- * license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright
- * ownership. Elasticsearch licenses this file to you under
- * the Apache License, Version 2.0 (the "License"); you may
- * not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-
-package org.elasticsearch.common.lucene;
-
-import org.apache.lucene.index.LeafReaderContext;
-import org.apache.lucene.search.*;
-import org.elasticsearch.common.lucene.search.XCollector;
-
-import java.io.IOException;
-
-/**
- *
- */
-public class MultiCollector extends SimpleCollector implements XCollector {
-
-    private final Collector collector;
-    private final Collector[] collectors;
-
-    private LeafCollector leafCollector;
-    private final LeafCollector[] leafCollectors;
-
-
-    public MultiCollector(Collector collector, Collector[] collectors) {
-        this.collector = collector;
-        this.collectors = collectors;
-        this.leafCollectors = new LeafCollector[collectors.length];
-    }
-
-    @Override
-    public void setScorer(Scorer scorer) throws IOException {
-        // always wrap it in a scorer wrapper
-        if (!(scorer instanceof ScoreCachingWrappingScorer)) {
-            scorer = new ScoreCachingWrappingScorer(scorer);
-        }
-        leafCollector.setScorer(scorer);
-        for (LeafCollector leafCollector : leafCollectors) {
-            leafCollector.setScorer(scorer);
-        }
-    }
-
-    @Override
-    public void collect(int doc) throws IOException {
-        leafCollector.collect(doc);
-        for (LeafCollector leafCollector : leafCollectors) {
-            leafCollector.collect(doc);
-        }
-    }
-
-    @Override
-    public void doSetNextReader(LeafReaderContext context) throws IOException {
-        leafCollector = collector.getLeafCollector(context);
-        for (int i = 0; i < collectors.length; i++) {
-            leafCollectors[i] = collectors[i].getLeafCollector(context);
-        }
-    }
-
-    @Override
-    public void postCollection() throws IOException {
-        if (collector instanceof XCollector) {
-            ((XCollector) collector).postCollection();
-        }
-        for (Collector collector : collectors) {
-            if (collector instanceof XCollector) {
-                ((XCollector) collector).postCollection();
-            }
-        }
-    }
-}

src/main/java/org/elasticsearch/search/internal/ContextIndexSearcher.java

@@ -24,13 +24,13 @@ import org.apache.lucene.search.Collector;
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.search.FilteredQuery;
 import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.MultiCollector;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TimeLimitingCollector;
 import org.apache.lucene.search.Weight;
 import org.elasticsearch.common.lease.Releasable;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.common.lucene.MinimumScoreCollector;
-import org.elasticsearch.common.lucene.MultiCollector;
 import org.elasticsearch.common.lucene.search.FilteredCollector;
 import org.elasticsearch.common.lucene.search.XCollector;
 import org.elasticsearch.index.engine.Engine;
@@ -151,7 +151,9 @@ public class ContextIndexSearcher extends IndexSearcher implements Releasable {
                 collector = new FilteredCollector(collector, searchContext.parsedPostFilter().filter());
             }
             if (queryCollectors != null && !queryCollectors.isEmpty()) {
-                collector = new MultiCollector(collector, queryCollectors.toArray(new Collector[queryCollectors.size()]));
+                ArrayList<Collector> allCollectors = new ArrayList<>(queryCollectors);
+                allCollectors.add(collector);
+                collector = MultiCollector.wrap(allCollectors);
             }
 
             // apply the minimum score after multi collector so we filter aggs as well