Lucene example source code file (QualityQueriesFinder.java)

This example Lucene source code file (QualityQueriesFinder.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

description, file, io, ioexception, ioexception, priorityqueue, qualityqueriesfinder, qualityqueriesfinder, string, string, term, termdf, termdf, termenum, termsdfqueue

The Lucene QualityQueriesFinder.java source code

/**
 * 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.benchmark.quality.utils;

import java.io.File;
import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.PriorityQueue;

/**
 * Suggest Quality queries based on an index contents.
 * Utility class, used for making quality test benchmarks.
 */
public class QualityQueriesFinder {

  private static final String newline = System.getProperty("line.separator");
  private Directory dir;
  
  /**
   * Constructor over a directory containing the index.
   * @param dir directory containing the index we search for the quality test. 
   */
  private QualityQueriesFinder(Directory dir) {
    this.dir = dir;
  }

  /**
   * @param args {index-dir}
   * @throws IOException  if cannot access the index.
   */
  public static void main(String[] args) throws IOException {
    if (args.length<1) {
      System.err.println("Usage: java QualityQueriesFinder <index-dir>");
      System.exit(1);
    }
    QualityQueriesFinder qqf = new QualityQueriesFinder(FSDirectory.open(new File(args[0])));
    String q[] = qqf.bestQueries("body",20);
    for (int i=0; i<q.length; i++) {
      System.out.println(newline+formatQueryAsTrecTopic(i,q[i],null,null));
    }
  }

  private String [] bestQueries(String field,int numQueries) throws IOException {
    String words[] = bestTerms("body",4*numQueries);
    int n = words.length;
    int m = n/4;
    String res[] = new String[m];
    for (int i=0; i<res.length; i++) {
      res[i] = words[i] + " " + words[m+i]+ "  " + words[n-1-m-i]  + " " + words[n-1-i];
      //System.out.println("query["+i+"]:  "+res[i]);
    }
    return res;
  }
  
  private static String formatQueryAsTrecTopic (int qnum, String title, String description, String narrative) {
    return 
      "<top>" + newline +
      "<num> Number: " + qnum             + newline + newline + 
      "<title> " + (title==null?"":title) + newline + newline + 
      "<desc> Description:"               + newline +
      (description==null?"":description)  + newline + newline +
      "<narr> Narrative:"                 + newline +
      (narrative==null?"":narrative)      + newline + newline +
      "</top>";
  }
  
  private String [] bestTerms(String field,int numTerms) throws IOException {
    PriorityQueue<TermDf> pq = new TermsDfQueue(numTerms);
    IndexReader ir = IndexReader.open(dir, true);
    try {
      int threshold = ir.maxDoc() / 10; // ignore words too common.
      TermEnum terms = ir.terms(new Term(field,""));
      while (terms.next()) {
        if (!field.equals(terms.term().field())) {
          break;
        }
        int df = terms.docFreq();
        if (df<threshold) {
          String ttxt = terms.term().text();
          pq.insertWithOverflow(new TermDf(ttxt,df));
        }
      }
    } finally {
      ir.close();
    }
    String res[] = new String[pq.size()];
    int i = 0;
    while (pq.size()>0) {
      TermDf tdf = pq.pop(); 
      res[i++] = tdf.word;
      System.out.println(i+".   word:  "+tdf.df+"   "+tdf.word);
    }
    return res;
  }

  private static class TermDf {
    String word;
    int df;
    TermDf (String word, int freq) {
      this.word = word;
      this.df = freq;
    }
  }
  
  private static class TermsDfQueue extends PriorityQueue<TermDf> {
    TermsDfQueue (int maxSize) {
      initialize(maxSize);
    }
    @Override
    protected boolean lessThan(TermDf tf1, TermDf tf2) {
      return tf1.df < tf2.df;
    }
  }
  
}