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Lucene example source code file (MultiTermQueryWrapperFilter.java)

This example Lucene source code file (MultiTermQueryWrapperFilter.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

docidset, io, ioexception, multitermquery, multitermquerywrapperfilter, multitermquerywrapperfilter, object, object, openbitset, override, override, q, string, term, termenum

The Lucene MultiTermQueryWrapperFilter.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.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.util.OpenBitSet;

/**
 * A wrapper for {@link MultiTermQuery}, that exposes its
 * functionality as a {@link Filter}.
 * <P>
 * <code>MultiTermQueryWrapperFilter is not designed to
 * be used by itself. Normally you subclass it to provide a Filter
 * counterpart for a {@link MultiTermQuery} subclass.
 * <P>
 * For example, {@link TermRangeFilter} and {@link PrefixFilter} extend
 * <code>MultiTermQueryWrapperFilter.
 * This class also provides the functionality behind
 * {@link MultiTermQuery#CONSTANT_SCORE_FILTER_REWRITE};
 * this is why it is not abstract.
 */
public class MultiTermQueryWrapperFilter<Q extends MultiTermQuery> extends Filter {
    
  protected final Q query;

  /**
   * Wrap a {@link MultiTermQuery} as a Filter.
   */
  protected MultiTermQueryWrapperFilter(Q query) {
      this.query = query;
  }
  
  @Override
  public String toString() {
    // query.toString should be ok for the filter, too, if the query boost is 1.0f
    return query.toString();
  }

  @Override
  public final boolean equals(final Object o) {
    if (o==this) return true;
    if (o==null) return false;
    if (this.getClass().equals(o.getClass())) {
      return this.query.equals( ((MultiTermQueryWrapperFilter)o).query );
    }
    return false;
  }

  @Override
  public final int hashCode() {
    return query.hashCode();
  }
  
  /**
   * Expert: Return the number of unique terms visited during execution of the filter.
   * If there are many of them, you may consider using another filter type
   * or optimize your total term count in index.
   * <p>This method is not thread safe, be sure to only call it when no filter is running!
   * If you re-use the same filter instance for another
   * search, be sure to first reset the term counter
   * with {@link #clearTotalNumberOfTerms}.
   * @see #clearTotalNumberOfTerms
   */
  public int getTotalNumberOfTerms() {
    return query.getTotalNumberOfTerms();
  }
  
  /**
   * Expert: Resets the counting of unique terms.
   * Do this before executing the filter.
   * @see #getTotalNumberOfTerms
   */
  public void clearTotalNumberOfTerms() {
    query.clearTotalNumberOfTerms();
  }
  
  /**
   * Returns a DocIdSet with documents that should be
   * permitted in search results.
   */
  @Override
  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
    final TermEnum enumerator = query.getEnum(reader);
    try {
      // if current term in enum is null, the enum is empty -> shortcut
      if (enumerator.term() == null)
        return DocIdSet.EMPTY_DOCIDSET;
      // else fill into a OpenBitSet
      final OpenBitSet bitSet = new OpenBitSet(reader.maxDoc());
      final int[] docs = new int[32];
      final int[] freqs = new int[32];
      TermDocs termDocs = reader.termDocs();
      try {
        int termCount = 0;
        do {
          Term term = enumerator.term();
          if (term == null)
            break;
          termCount++;
          termDocs.seek(term);
          while (true) {
            final int count = termDocs.read(docs, freqs);
            if (count != 0) {
              for(int i=0;i<count;i++) {
                bitSet.set(docs[i]);
              }
            } else {
              break;
            }
          }
        } while (enumerator.next());

        query.incTotalNumberOfTerms(termCount);

      } finally {
        termDocs.close();
      }
      return bitSet;
    } finally {
      enumerator.close();
    }
  }

}

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