Lucene example source code file (DistanceQuery.java)

This example Lucene source code file (DistanceQuery.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

basicqueryfactory, distancequery, distancesubquery, distancesubquery, io, ioexception, ioexception, iterator, override, query, query, spannearclausefactory, spannearquery, string, string, util

The Lucene DistanceQuery.java source code

package org.apache.lucene.queryParser.surround.query;
/**
 * 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.util.List;
import java.util.Iterator;

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.spans.SpanNearQuery;
import org.apache.lucene.search.spans.SpanQuery;

public class DistanceQuery extends ComposedQuery implements DistanceSubQuery {
  public DistanceQuery(
      List<SrndQuery> queries,
      boolean infix,
      int opDistance,
      String opName,
      boolean ordered) {
    super(queries, infix, opName);
    this.opDistance = opDistance; /* the distance indicated in the operator */
    this.ordered = ordered;
  }

  private int opDistance;
  public int getOpDistance() {return opDistance;}
  
  private boolean ordered;
  public boolean subQueriesOrdered() {return ordered;}
  
  public String distanceSubQueryNotAllowed() {
    Iterator<?> sqi = getSubQueriesIterator();
    while (sqi.hasNext()) {
      Object leq = sqi.next();
      if (leq instanceof DistanceSubQuery) {
        DistanceSubQuery dsq = (DistanceSubQuery) leq;
        String m = dsq.distanceSubQueryNotAllowed();
        if (m != null) {
          return m; 
        }
      } else {
        return "Operator " + getOperatorName() + " does not allow subquery " + leq.toString();
      }
    }
    return null; /* subqueries acceptable */
  }

  
  public void addSpanQueries(SpanNearClauseFactory sncf) throws IOException {
    Query snq = getSpanNearQuery(sncf.getIndexReader(),
                                  sncf.getFieldName(),
                                  getWeight(),
                                  sncf.getBasicQueryFactory());
    sncf.addSpanNearQuery(snq);
  }

  @Override
  public Query makeLuceneQueryFieldNoBoost(final String fieldName, final BasicQueryFactory qf) {
    return new Query () {
      
      @Override
      public String toString(String fn) {
        return getClass().toString() + " " + fieldName + " (" + fn + "?)";
      }
      
      @Override
      public Query rewrite(IndexReader reader) throws IOException {
        return getSpanNearQuery(reader, fieldName, getBoost(), qf);
      }
      
    };
  }
  
  public Query getSpanNearQuery(
          IndexReader reader,
          String fieldName,
          float boost,
          BasicQueryFactory qf) throws IOException {
    SpanQuery[] spanNearClauses = new SpanQuery[getNrSubQueries()];
    Iterator<?> sqi = getSubQueriesIterator();
    int qi = 0;
    while (sqi.hasNext()) {
      SpanNearClauseFactory sncf = new SpanNearClauseFactory(reader, fieldName, qf);
      
      ((DistanceSubQuery)sqi.next()).addSpanQueries(sncf);
      if (sncf.size() == 0) { /* distance operator requires all sub queries */
        while (sqi.hasNext()) { /* produce evt. error messages but ignore results */
          ((DistanceSubQuery)sqi.next()).addSpanQueries(sncf);
          sncf.clear();
        }
        return SrndQuery.theEmptyLcnQuery;
      }
      
      spanNearClauses[qi] = sncf.makeSpanNearClause();

      qi++;
    }
    
    SpanNearQuery r = new SpanNearQuery(spanNearClauses, getOpDistance() - 1, subQueriesOrdered());
    r.setBoost(boost);
    return r;
  }
}