Introduce LargeNumHitsTopDocsCollectorManager

lucene/CHANGES.txt

@@ -89,6 +89,8 @@ Improvements
 
 * GITHUB#15453: Avoid unnecessary sorting and instantiations in readMapOfStrings. (Benjamin Lerer)
 
+* GITHUB#15660: Introduce LargeNumHitsTopDocsCollectorManager to parallelize search when using LargeNumHitsTopDocsCollector. (Binlong Gao)
+
 Optimizations
 ---------------------
 * GITHUB#13782: Replace handwritten loops compare with Arrays.compareUnsigned in TermsEnum and TermsEnumFrame classes. (Zhou Hui)

lucene/sandbox/src/java/org/apache/lucene/sandbox/search/LargeNumHitsTopDocsCollectorManager.java

@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.apache.lucene.sandbox.search;
+
+import java.io.IOException;
+import java.util.Collection;
+import org.apache.lucene.search.CollectorManager;
+import org.apache.lucene.search.TopDocs;
+
+/**
+ * CollectorManager for {@link LargeNumHitsTopDocsCollector} that enables concurrent collection of
+ * top docs across multiple segments.
+ */
+public class LargeNumHitsTopDocsCollectorManager
+    implements CollectorManager<LargeNumHitsTopDocsCollector, TopDocs> {
+  private final int numHits;
+
+  /**
+   * Creates a new {@link LargeNumHitsTopDocsCollectorManager} given the number of hits to collect.
+   *
+   * @param numHits the number of results to collect.
+   */
+  public LargeNumHitsTopDocsCollectorManager(int numHits) {
+    if (numHits <= 0) {
+      throw new IllegalArgumentException("numHits must be > 0, got " + numHits);
+    }
+    this.numHits = numHits;
+  }
+
+  @Override
+  public LargeNumHitsTopDocsCollector newCollector() {
+    return new LargeNumHitsTopDocsCollector(numHits);
+  }
+
+  @Override
+  public TopDocs reduce(Collection<LargeNumHitsTopDocsCollector> collectors) throws IOException {
+    final TopDocs[] topDocs = new TopDocs[collectors.size()];
+    int i = 0;
+    for (LargeNumHitsTopDocsCollector collector : collectors) {
+      topDocs[i++] = collector.topDocs();
+    }
+    return TopDocs.merge(0, numHits, topDocs);
+  }
+}

lucene/sandbox/src/test/org/apache/lucene/sandbox/search/TestLargeNumHitsTopDocsCollector.java

@@ -82,74 +82,66 @@ public void testRequestLessHitsThanCollected() throws Exception {
 
   public void testIllegalArguments() throws IOException {
     IndexSearcher searcher = newSearcher(reader);
-    LargeNumHitsTopDocsCollector largeCollector = new LargeNumHitsTopDocsCollector(15);
+    LargeNumHitsTopDocsCollectorManager largeCollectorManager =
+        new LargeNumHitsTopDocsCollectorManager(15);
     TopScoreDocCollectorManager regularCollectorManager =
         new TopScoreDocCollectorManager(15, Integer.MAX_VALUE);
 
-    searcher.search(testQuery, largeCollector);
-    TopDocs topDocs = searcher.search(testQuery, regularCollectorManager);
+    TopDocs largeTopDocs = searcher.search(testQuery, largeCollectorManager);
+    TopDocs regularTopDocs = searcher.search(testQuery, regularCollectorManager);
 
-    assertEquals(largeCollector.totalHits, topDocs.totalHits.value());
+    assertEquals(largeTopDocs.totalHits.value(), regularTopDocs.totalHits.value());
 
+    LargeNumHitsTopDocsCollector collector = largeCollectorManager.newCollector();
     IllegalArgumentException expected =
-        expectThrows(
-            IllegalArgumentException.class,
-            () -> {
-              largeCollector.topDocs(350_000);
-            });
+        expectThrows(IllegalArgumentException.class, () -> collector.topDocs(350_000));
 
     assertTrue(expected.getMessage().contains("Incorrect number of hits requested"));
   }
 
   public void testNoPQBuild() throws IOException {
     IndexSearcher searcher = newSearcher(reader);
-    LargeNumHitsTopDocsCollector largeCollector = new LargeNumHitsTopDocsCollector(250_000);
+    LargeNumHitsTopDocsCollectorManager largeCollectorManager =
+        new LargeNumHitsTopDocsCollectorManager(250_000);
     TopScoreDocCollectorManager regularCollectorManager =
         new TopScoreDocCollectorManager(reader.numDocs(), Integer.MAX_VALUE);
 
-    searcher.search(testQuery, largeCollector);
-    TopDocs topDocs = searcher.search(testQuery, regularCollectorManager);
+    TopDocs largeTopDocs = searcher.search(testQuery, largeCollectorManager);
+    TopDocs regularTopDocs = searcher.search(testQuery, regularCollectorManager);
 
-    assertEquals(largeCollector.totalHits, topDocs.totalHits.value());
-
-    assertNull(largeCollector.pq);
-    assertNull(largeCollector.pqTop);
+    assertEquals(largeTopDocs.totalHits.value(), regularTopDocs.totalHits.value());
+    CheckHits.checkEqual(testQuery, largeTopDocs.scoreDocs, regularTopDocs.scoreDocs);
   }
 
   public void testPQBuild() throws IOException {
     IndexSearcher searcher = newSearcher(reader);
-    LargeNumHitsTopDocsCollector largeCollector = new LargeNumHitsTopDocsCollector(50);
+    LargeNumHitsTopDocsCollectorManager largeCollectorManager =
+        new LargeNumHitsTopDocsCollectorManager(50);
     TopScoreDocCollectorManager regularCollectorManager =
         new TopScoreDocCollectorManager(50, Integer.MAX_VALUE);
 
-    searcher.search(testQuery, largeCollector);
-    TopDocs topDocs = searcher.search(testQuery, regularCollectorManager);
-
-    assertEquals(largeCollector.totalHits, topDocs.totalHits.value());
+    TopDocs largeTopDocs = searcher.search(testQuery, largeCollectorManager);
+    TopDocs regularTopDocs = searcher.search(testQuery, regularCollectorManager);
 
-    assertNotNull(largeCollector.pq);
-    assertNotNull(largeCollector.pqTop);
+    assertEquals(largeTopDocs.totalHits.value(), regularTopDocs.totalHits.value());
+    CheckHits.checkEqual(testQuery, largeTopDocs.scoreDocs, regularTopDocs.scoreDocs);
   }
 
   public void testNoPQHitsOrder() throws IOException {
     IndexSearcher searcher = newSearcher(reader);
-    LargeNumHitsTopDocsCollector largeCollector = new LargeNumHitsTopDocsCollector(250_000);
+    LargeNumHitsTopDocsCollectorManager largeCollectorManager =
+        new LargeNumHitsTopDocsCollectorManager(250_000);
     TopScoreDocCollectorManager regularCollectorManager =
         new TopScoreDocCollectorManager(reader.numDocs(), Integer.MAX_VALUE);
 
-    searcher.search(testQuery, largeCollector);
-    TopDocs topDocs = searcher.search(testQuery, regularCollectorManager);
-
-    assertEquals(largeCollector.totalHits, topDocs.totalHits.value());
+    TopDocs largeTopDocs = searcher.search(testQuery, largeCollectorManager);
+    TopDocs regularTopDocs = searcher.search(testQuery, regularCollectorManager);
 
-    assertNull(largeCollector.pq);
-    assertNull(largeCollector.pqTop);
+    assertEquals(largeTopDocs.totalHits.value(), regularTopDocs.totalHits.value());
 
-    topDocs = largeCollector.topDocs();
-
-    if (topDocs.scoreDocs.length > 0) {
-      float preScore = topDocs.scoreDocs[0].score;
-      for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
+    if (largeTopDocs.scoreDocs.length > 0) {
+      float preScore = largeTopDocs.scoreDocs[0].score;
+      for (ScoreDoc scoreDoc : largeTopDocs.scoreDocs) {
         assert scoreDoc.score <= preScore;
         preScore = scoreDoc.score;
       }
@@ -158,17 +150,16 @@ public void testNoPQHitsOrder() throws IOException {
 
   private void runNumHits(int numHits) throws IOException {
     IndexSearcher searcher = newSearcher(reader);
-    LargeNumHitsTopDocsCollector largeCollector = new LargeNumHitsTopDocsCollector(numHits);
+    LargeNumHitsTopDocsCollectorManager largeCollectorManager =
+        new LargeNumHitsTopDocsCollectorManager(numHits);
     TopScoreDocCollectorManager regularCollectorManager =
         new TopScoreDocCollectorManager(numHits, Integer.MAX_VALUE);
 
-    searcher.search(testQuery, largeCollector);
-
-    TopDocs firstTopDocs = largeCollector.topDocs();
-    TopDocs secondTopDocs = searcher.search(testQuery, regularCollectorManager);
+    TopDocs largeTopDocs = searcher.search(testQuery, largeCollectorManager);
+    TopDocs regularTopDocs = searcher.search(testQuery, regularCollectorManager);
 
-    assertEquals(largeCollector.totalHits, secondTopDocs.totalHits.value());
-    assertEquals(firstTopDocs.scoreDocs.length, secondTopDocs.scoreDocs.length);
-    CheckHits.checkEqual(testQuery, firstTopDocs.scoreDocs, secondTopDocs.scoreDocs);
+    assertEquals(largeTopDocs.totalHits.value(), regularTopDocs.totalHits.value());
+    assertEquals(largeTopDocs.scoreDocs.length, regularTopDocs.scoreDocs.length);
+    CheckHits.checkEqual(testQuery, largeTopDocs.scoreDocs, regularTopDocs.scoreDocs);
   }
 }