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Lucene example source code file (TopDocs.java)

This example Lucene source code file (TopDocs.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

fielddoc, fielddoc, illegalargumentexception, io, ioexception, mergesortqueue, priorityqueue, scoredoc, scoredoc, scoremergesortqueue, shardref, shardref, sortfield, topdocs, topdocs

The Lucene TopDocs.java source code

package org.apache.lucene.search;

/**
 * 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.
 */

import java.io.IOException;

import org.apache.lucene.util.PriorityQueue;

/** Represents hits returned by {@link
 * Searcher#search(Query,Filter,int)} and {@link
 * Searcher#search(Query,int)}. */
public class TopDocs implements java.io.Serializable {

  /** The total number of hits for the query. */
  public int totalHits;

  /** The top hits for the query. */
  public ScoreDoc[] scoreDocs;

  /** Stores the maximum score value encountered, needed for normalizing. */
  private float maxScore;
  
  /**
   * Returns the maximum score value encountered. Note that in case
   * scores are not tracked, this returns {@link Float#NaN}.
   */
  public float getMaxScore() {
    return maxScore;
  }
  
  /** Sets the maximum score value encountered. */
  public void setMaxScore(float maxScore) {
    this.maxScore=maxScore;
  }

  /** Constructs a TopDocs with a default maxScore=Float.NaN. */
  TopDocs(int totalHits, ScoreDoc[] scoreDocs) {
    this(totalHits, scoreDocs, Float.NaN);
  }

  public TopDocs(int totalHits, ScoreDoc[] scoreDocs, float maxScore) {
    this.totalHits = totalHits;
    this.scoreDocs = scoreDocs;
    this.maxScore = maxScore;
  }

  // Refers to one hit:
  private static class ShardRef {
    // Which shard (index into shardHits[]):
    final int shardIndex;

    // Which hit within the shard:
    int hitIndex;

    public ShardRef(int shardIndex) {
      this.shardIndex = shardIndex;
    }

    @Override
    public String toString() {
      return "ShardRef(shardIndex=" + shardIndex + " hitIndex=" + hitIndex + ")";
    }
  };

  // Specialized MergeSortQueue that just merges by
  // relevance score, descending:
  private static class ScoreMergeSortQueue extends PriorityQueue<ShardRef> {
    final ScoreDoc[][] shardHits;

    public ScoreMergeSortQueue(TopDocs[] shardHits) {
      initialize(shardHits.length);
      this.shardHits = new ScoreDoc[shardHits.length][];
      for(int shardIDX=0;shardIDX<shardHits.length;shardIDX++) {
        this.shardHits[shardIDX] = shardHits[shardIDX].scoreDocs;
      }
    }

    // Returns true if first is < second
    public boolean lessThan(ShardRef first, ShardRef second) {
      assert first != second;
      final float firstScore = shardHits[first.shardIndex][first.hitIndex].score;
      final float secondScore = shardHits[second.shardIndex][second.hitIndex].score;

      if (firstScore < secondScore) {
        return false;
      } else if (firstScore > secondScore) {
        return true;
      } else {
        // Tie break: earlier shard wins
        if (first.shardIndex < second.shardIndex) {
          return true;
        } else if (first.shardIndex > second.shardIndex) {
          return false;
        } else {
          // Tie break in same shard: resolve however the
          // shard had resolved it:
          assert first.hitIndex != second.hitIndex;
          return first.hitIndex < second.hitIndex;
        }
      }
    }
  }

  private static class MergeSortQueue extends PriorityQueue<ShardRef> {
    // These are really FieldDoc instances:
    final ScoreDoc[][] shardHits;
    final FieldComparator[] comparators;
    final int[] reverseMul;

    public MergeSortQueue(Sort sort, TopDocs[] shardHits) throws IOException {
      initialize(shardHits.length);
      this.shardHits = new ScoreDoc[shardHits.length][];
      for(int shardIDX=0;shardIDX<shardHits.length;shardIDX++) {
        final ScoreDoc[] shard = shardHits[shardIDX].scoreDocs;
        //System.out.println("  init shardIdx=" + shardIDX + " hits=" + shard);
        if (shard != null) {
          this.shardHits[shardIDX] = shard;
          // Fail gracefully if API is misused:
          for(int hitIDX=0;hitIDX<shard.length;hitIDX++) {
            final ScoreDoc sd = shard[hitIDX];
            if (!(sd instanceof FieldDoc)) {
              throw new IllegalArgumentException("shard " + shardIDX + " was not sorted by the provided Sort (expected FieldDoc but got ScoreDoc)");
            }
            final FieldDoc fd = (FieldDoc) sd;
            if (fd.fields == null) {
              throw new IllegalArgumentException("shard " + shardIDX + " did not set sort field values (FieldDoc.fields is null); you must pass fillFields=true to IndexSearcher.search on each shard");
            }
          }
        }
      }

      final SortField[] sortFields = sort.getSort();
      comparators = new FieldComparator[sortFields.length];
      reverseMul = new int[sortFields.length];
      for(int compIDX=0;compIDX<sortFields.length;compIDX++) {
        final SortField sortField = sortFields[compIDX];
        comparators[compIDX] = sortField.getComparator(1, compIDX);
        reverseMul[compIDX] = sortField.getReverse() ? -1 : 1;
      }
    }

    // Returns true if first is < second
    @SuppressWarnings("unchecked")
    public boolean lessThan(ShardRef first, ShardRef second) {
      assert first != second;
      final FieldDoc firstFD = (FieldDoc) shardHits[first.shardIndex][first.hitIndex];
      final FieldDoc secondFD = (FieldDoc) shardHits[second.shardIndex][second.hitIndex];
      //System.out.println("  lessThan:\n     first=" + first + " doc=" + firstFD.doc + " score=" + firstFD.score + "\n    second=" + second + " doc=" + secondFD.doc + " score=" + secondFD.score);

      for(int compIDX=0;compIDX<comparators.length;compIDX++) {
        final FieldComparator comp = comparators[compIDX];
        //System.out.println("    cmp idx=" + compIDX + " cmp1=" + firstFD.fields[compIDX] + " cmp2=" + secondFD.fields[compIDX] + " reverse=" + reverseMul[compIDX]);

        final int cmp = reverseMul[compIDX] * comp.compareValues(firstFD.fields[compIDX], secondFD.fields[compIDX]);
        
        if (cmp != 0) {
          //System.out.println("    return " + (cmp < 0));
          return cmp < 0;
        }
      }

      // Tie break: earlier shard wins
      if (first.shardIndex < second.shardIndex) {
        //System.out.println("    return tb true");
        return true;
      } else if (first.shardIndex > second.shardIndex) {
        //System.out.println("    return tb false");
        return false;
      } else {
        // Tie break in same shard: resolve however the
        // shard had resolved it:
        //System.out.println("    return tb " + (first.hitIndex < second.hitIndex));
        assert first.hitIndex != second.hitIndex;
        return first.hitIndex < second.hitIndex;
      }
    }
  }

  /** Returns a new TopDocs, containing topN results across
   *  the provided TopDocs, sorting by the specified {@link
   *  Sort}.  Each of the TopDocs must have been sorted by
   *  the same Sort, and sort field values must have been
   *  filled (ie, <code>fillFields=true must be
   *  passed to {@link
   *  TopFieldCollector#create}.
   *
   * <p>Pass sort=null to merge sort by score descending.
   *
   * @lucene.experimental */
  public static TopDocs merge(Sort sort, int topN, TopDocs[] shardHits) throws IOException {

    final PriorityQueue<ShardRef> queue;
    if (sort == null) {
      queue = new ScoreMergeSortQueue(shardHits);
    } else {
      queue = new MergeSortQueue(sort, shardHits);
    }

    int totalHitCount = 0;
    float maxScore = Float.MIN_VALUE;
    for(int shardIDX=0;shardIDX<shardHits.length;shardIDX++) {
      final TopDocs shard = shardHits[shardIDX];
      if (shard.scoreDocs != null && shard.scoreDocs.length > 0) {
        totalHitCount += shard.totalHits;
        queue.add(new ShardRef(shardIDX));
        maxScore = Math.max(maxScore, shard.getMaxScore());
        //System.out.println("  maxScore now " + maxScore + " vs " + shard.getMaxScore());
      }
    }

    final ScoreDoc[] hits = new ScoreDoc[Math.min(topN, totalHitCount)];

    int hitUpto = 0;
    while(hitUpto < hits.length) {
      assert queue.size() > 0;
      ShardRef ref = queue.pop();
      final ScoreDoc hit = shardHits[ref.shardIndex].scoreDocs[ref.hitIndex++];
      if (sort == null) {
        hits[hitUpto] = new ScoreDoc(hit.doc, hit.score, ref.shardIndex);
      } else {
        hits[hitUpto] = new FieldDoc(hit.doc, hit.score, ((FieldDoc) hit).fields, ref.shardIndex);
      }

      //System.out.println("  hitUpto=" + hitUpto);
      //System.out.println("    doc=" + hits[hitUpto].doc + " score=" + hits[hitUpto].score);

      hitUpto++;

      if (ref.hitIndex < shardHits[ref.shardIndex].scoreDocs.length) {
        // Not done with this these TopDocs yet:
        queue.add(ref);
      }
    }

    if (sort == null) {
      return new TopDocs(totalHitCount, hits, maxScore);
    } else {
      return new TopFieldDocs(totalHitCount, hits, sort.getSort(), maxScore);
    }
  }
}

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