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Lucene example source code file (ConstantScoreAutoRewrite.java)

This example Lucene source code file (ConstantScoreAutoRewrite.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

arraylist, booleanquery, booleanquery, constantscoreautorewrite, constantscoreautorewrite, cutofftermcollector, cutofftermcollector, default_doc_count_percent, default_term_count_cutoff, indexreader, io, ioexception, override, override, query, util

The Lucene ConstantScoreAutoRewrite.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 java.util.ArrayList;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;

class ConstantScoreAutoRewrite extends TermCollectingRewrite<BooleanQuery> {

  // Defaults derived from rough tests with a 20.0 million
  // doc Wikipedia index.  With more than 350 terms in the
  // query, the filter method is fastest:
  public static int DEFAULT_TERM_COUNT_CUTOFF = 350;

  // If the query will hit more than 1 in 1000 of the docs
  // in the index (0.1%), the filter method is fastest:
  public static double DEFAULT_DOC_COUNT_PERCENT = 0.1;

  private int termCountCutoff = DEFAULT_TERM_COUNT_CUTOFF;
  private double docCountPercent = DEFAULT_DOC_COUNT_PERCENT;

  /** If the number of terms in this query is equal to or
   *  larger than this setting then {@link
   *  #CONSTANT_SCORE_FILTER_REWRITE} is used. */
  public void setTermCountCutoff(int count) {
    termCountCutoff = count;
  }

  /** @see #setTermCountCutoff */
  public int getTermCountCutoff() {
    return termCountCutoff;
  }

  /** If the number of documents to be visited in the
   *  postings exceeds this specified percentage of the
   *  maxDoc() for the index, then {@link
   *  #CONSTANT_SCORE_FILTER_REWRITE} is used.
   *  @param percent 0.0 to 100.0 */
  public void setDocCountPercent(double percent) {
    docCountPercent = percent;
  }

  /** @see #setDocCountPercent */
  public double getDocCountPercent() {
    return docCountPercent;
  }

  @Override
  protected BooleanQuery getTopLevelQuery() {
    return new BooleanQuery(true);
  }
  
  @Override
  protected void addClause(BooleanQuery topLevel, Term term, float boost /*ignored*/) {
    topLevel.add(new TermQuery(term), BooleanClause.Occur.SHOULD);
  }

  @Override
  public Query rewrite(final IndexReader reader, final MultiTermQuery query) throws IOException {

    // Get the enum and start visiting terms.  If we
    // exhaust the enum before hitting either of the
    // cutoffs, we use ConstantBooleanQueryRewrite; else,
    // ConstantFilterRewrite:
    final int docCountCutoff = (int) ((docCountPercent / 100.) * reader.maxDoc());
    final int termCountLimit = Math.min(BooleanQuery.getMaxClauseCount(), termCountCutoff);

    final CutOffTermCollector col = new CutOffTermCollector(reader, docCountCutoff, termCountLimit);
    collectTerms(reader, query, col);
    
    if (col.hasCutOff) {
      return MultiTermQuery.CONSTANT_SCORE_FILTER_REWRITE.rewrite(reader, query);
    } else {
      final Query result;
      if (col.pendingTerms.isEmpty()) {
        result = getTopLevelQuery();
      } else {
        BooleanQuery bq = getTopLevelQuery();
        for(Term term : col.pendingTerms) {
          addClause(bq, term, 1.0f);
        }
        // Strip scores
        result = new ConstantScoreQuery(bq);
        result.setBoost(query.getBoost());
      }
      query.incTotalNumberOfTerms(col.pendingTerms.size());
      return result;
    }
  }
  
  private static final class CutOffTermCollector implements TermCollector {
    CutOffTermCollector(IndexReader reader, int docCountCutoff, int termCountLimit) {
      this.reader = reader;
      this.docCountCutoff = docCountCutoff;
      this.termCountLimit = termCountLimit;
    }
  
    public boolean collect(Term t, float boost) throws IOException {
      pendingTerms.add(t);
      // Loading the TermInfo from the terms dict here
      // should not be costly, because 1) the
      // query/filter will load the TermInfo when it
      // runs, and 2) the terms dict has a cache:
      docVisitCount += reader.docFreq(t);
      if (pendingTerms.size() >= termCountLimit || docVisitCount >= docCountCutoff) {
        hasCutOff = true;
        return false;
      }
      return true;
    }
    
    int docVisitCount = 0;
    boolean hasCutOff = false;
    
    final IndexReader reader;
    final int docCountCutoff, termCountLimit;
    final ArrayList<Term> pendingTerms = new ArrayList();
  }

  @Override
  public int hashCode() {
    final int prime = 1279;
    return (int) (prime * termCountCutoff + Double.doubleToLongBits(docCountPercent));
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;

    ConstantScoreAutoRewrite other = (ConstantScoreAutoRewrite) obj;
    if (other.termCountCutoff != termCountCutoff) {
      return false;
    }

    if (Double.doubleToLongBits(other.docCountPercent) != Double.doubleToLongBits(docCountPercent)) {
      return false;
    }
    
    return true;
  }
}

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