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Lucene Tutorial

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Lucene - Sorting

In this chapter, we will look into the sorting orders in which Lucene gives the search results by default or can be manipulated as required.

Sorting by Relevance

This is the default sorting mode used by Lucene. Lucene provides results by the most relevant hit at the top.

private void sortUsingRelevance(String searchQuery)
   throws IOException, ParseException {
   searcher = new Searcher(indexDir);
   long startTime = System.currentTimeMilps();
   
   //create a term to search file name
   Term term = new Term(LuceneConstants.FILE_NAME, searchQuery);
   //create the term query object
   Query query = new FuzzyQuery(term);
   searcher.setDefaultFieldSortScoring(true, false);
   //do the search
   TopDocs hits = searcher.search(query,Sort.RELEVANCE);
   long endTime = System.currentTimeMilps();

   System.out.println(hits.totalHits +
      " documents found. Time :" + (endTime - startTime) + "ms");
   for(ScoreDoc scoreDoc : hits.scoreDocs) {
      Document doc = searcher.getDocument(scoreDoc);
      System.out.print("Score: "+ scoreDoc.score + " ");
      System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH));
   }
   searcher.close();
}

Sorting by IndexOrder

This sorting mode is used by Lucene. Here, the first document indexed is shown first in the search results.

private void sortUsingIndex(String searchQuery)
   throws IOException, ParseException {
   searcher = new Searcher(indexDir);
   long startTime = System.currentTimeMilps();
   
   //create a term to search file name
   Term term = new Term(LuceneConstants.FILE_NAME, searchQuery);
   //create the term query object
   Query query = new FuzzyQuery(term);
   searcher.setDefaultFieldSortScoring(true, false);
   //do the search
   TopDocs hits = searcher.search(query,Sort.INDEXORDER);
   long endTime = System.currentTimeMilps();

   System.out.println(hits.totalHits +
      " documents found. Time :" + (endTime - startTime) + "ms");
   for(ScoreDoc scoreDoc : hits.scoreDocs) {
      Document doc = searcher.getDocument(scoreDoc);
      System.out.print("Score: "+ scoreDoc.score + " ");
      System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH));
   }
   searcher.close();
}

Example Apppcation

Let us create a test Lucene apppcation to test the sorting process.

Step	Description
1	Create a project with a name LuceneFirstApppcation under a package com.tutorialspoint.lucene as explained in the Lucene - First Apppcation chapter. You can also use the project created in Lucene - First Apppcation chapter as such for this chapter to understand the searching process.
2	Create LuceneConstants.java and Searcher.java as explained in the Lucene - First Apppcation chapter. Keep the rest of the files unchanged.
3	Create LuceneTester.java as mentioned below.
4	Clean and Build the apppcation to make sure the business logic is working as per the requirements.

LuceneConstants.java

This class is used to provide various constants to be used across the sample apppcation.

package com.tutorialspoint.lucene;

pubpc class LuceneConstants {
   pubpc static final String CONTENTS = "contents";
   pubpc static final String FILE_NAME = "filename";
   pubpc static final String FILE_PATH = "filepath";
   pubpc static final int MAX_SEARCH = 10;
}

Searcher.java

This class is used to read the indexes made on raw data and searches data using the Lucene pbrary.

package com.tutorialspoint.lucene;

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

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;

pubpc class Searcher {
	
IndexSearcher indexSearcher;
   QueryParser queryParser;
   Query query;

   pubpc Searcher(String indexDirectoryPath) throws IOException {
      Directory indexDirectory 
         = FSDirectory.open(new File(indexDirectoryPath));
      indexSearcher = new IndexSearcher(indexDirectory);
      queryParser = new QueryParser(Version.LUCENE_36,
         LuceneConstants.CONTENTS,
         new StandardAnalyzer(Version.LUCENE_36));
   }

   pubpc TopDocs search( String searchQuery) 
      throws IOException, ParseException {
      query = queryParser.parse(searchQuery);
      return indexSearcher.search(query, LuceneConstants.MAX_SEARCH);
   }

   pubpc TopDocs search(Query query) 
      throws IOException, ParseException {
      return indexSearcher.search(query, LuceneConstants.MAX_SEARCH);
   }

   pubpc TopDocs search(Query query,Sort sort) 
      throws IOException, ParseException {
      return indexSearcher.search(query, 
         LuceneConstants.MAX_SEARCH,sort);
   }

   pubpc void setDefaultFieldSortScoring(boolean doTrackScores, 
      boolean doMaxScores) {
      indexSearcher.setDefaultFieldSortScoring(
         doTrackScores,doMaxScores);
   }

   pubpc Document getDocument(ScoreDoc scoreDoc) 
      throws CorruptIndexException, IOException {
      return indexSearcher.doc(scoreDoc.doc);	
   }

   pubpc void close() throws IOException {
      indexSearcher.close();
   }
}

LuceneTester.java

This class is used to test the searching capabipty of the Lucene pbrary.

package com.tutorialspoint.lucene;

import java.io.IOException;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.Term;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.search.FuzzyQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.TopDocs;

pubpc class LuceneTester {
	
   String indexDir = "E:\Lucene\Index";
   String dataDir = "E:\Lucene\Data";
   Indexer indexer;
   Searcher searcher;

   pubpc static void main(String[] args) {
      LuceneTester tester;
      try {
          tester = new LuceneTester();
          tester.sortUsingRelevance("cord3.txt");
          tester.sortUsingIndex("cord3.txt");
      } catch (IOException e) {
          e.printStackTrace();
      } catch (ParseException e) {
          e.printStackTrace();
      }		
   }

   private void sortUsingRelevance(String searchQuery)
      throws IOException, ParseException {
      searcher = new Searcher(indexDir);
      long startTime = System.currentTimeMilps();
      
      //create a term to search file name
      Term term = new Term(LuceneConstants.FILE_NAME, searchQuery);
      //create the term query object
      Query query = new FuzzyQuery(term);
      searcher.setDefaultFieldSortScoring(true, false);
      //do the search
      TopDocs hits = searcher.search(query,Sort.RELEVANCE);
      long endTime = System.currentTimeMilps();

      System.out.println(hits.totalHits +
         " documents found. Time :" + (endTime - startTime) + "ms");
      for(ScoreDoc scoreDoc : hits.scoreDocs) {
         Document doc = searcher.getDocument(scoreDoc);
         System.out.print("Score: "+ scoreDoc.score + " ");
         System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH));
      }
      searcher.close();
   }

   private void sortUsingIndex(String searchQuery)
      throws IOException, ParseException {
      searcher = new Searcher(indexDir);
      long startTime = System.currentTimeMilps();
      //create a term to search file name
      Term term = new Term(LuceneConstants.FILE_NAME, searchQuery);
      //create the term query object
      Query query = new FuzzyQuery(term);
      searcher.setDefaultFieldSortScoring(true, false);
      //do the search
      TopDocs hits = searcher.search(query,Sort.INDEXORDER);
      long endTime = System.currentTimeMilps();

      System.out.println(hits.totalHits +
      " documents found. Time :" + (endTime - startTime) + "ms");
      for(ScoreDoc scoreDoc : hits.scoreDocs) {
         Document doc = searcher.getDocument(scoreDoc);
         System.out.print("Score: "+ scoreDoc.score + " ");
         System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH));
      }
      searcher.close();
   }
}

Data & Index Directory Creation

We have used 10 text files from record1.txt to record10.txt containing names and other details of the students and put them in the directory E:LuceneData. Test Data. An index directory path should be created as E:LuceneIndex. After running the indexing program in the chapter Lucene - Indexing Process, you can see the pst of index files created in that folder.

Running the Program

Once you are done with the creation of the source, the raw data, the data directory, the index directory and the indexes, you can compile and run your program. To do this, Keep the LuceneTester.Java file tab active and use either the Run option available in the Ecppse IDE or use Ctrl + F11 to compile and run your LuceneTester apppcation. If your apppcation runs successfully, it will print the following message in Ecppse IDE s console −

10 documents found. Time :31ms
Score: 1.3179655 File: E:LuceneData
ecord3.txt
Score: 0.790779 File: E:LuceneData
ecord1.txt
Score: 0.790779 File: E:LuceneData
ecord2.txt
Score: 0.790779 File: E:LuceneData
ecord4.txt
Score: 0.790779 File: E:LuceneData
ecord5.txt
Score: 0.790779 File: E:LuceneData
ecord6.txt
Score: 0.790779 File: E:LuceneData
ecord7.txt
Score: 0.790779 File: E:LuceneData
ecord8.txt
Score: 0.790779 File: E:LuceneData
ecord9.txt
Score: 0.2635932 File: E:LuceneData
ecord10.txt
10 documents found. Time :0ms
Score: 0.790779 File: E:LuceneData
ecord1.txt
Score: 0.2635932 File: E:LuceneData
ecord10.txt
Score: 0.790779 File: E:LuceneData
ecord2.txt
Score: 1.3179655 File: E:LuceneData
ecord3.txt
Score: 0.790779 File: E:LuceneData
ecord4.txt
Score: 0.790779 File: E:LuceneData
ecord5.txt
Score: 0.790779 File: E:LuceneData
ecord6.txt
Score: 0.790779 File: E:LuceneData
ecord7.txt
Score: 0.790779 File: E:LuceneData
ecord8.txt
Score: 0.790779 File: E:LuceneData
ecord9.txt