Lucene - RegexpQuery

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RegexpQuery class represents a Regular Expression based Query. RegexpQuery comparisons are quiet fast.

Class Declaration

Following is the declaration for org.apache.lucene.search.RegexpQuery class −

public class RegexpQuery
   extends AutomatonQuery

Class Fields

S.No.	Field & Description
1	static final AutomatonProvider DEFAULT_PROVIDER A provider that provides no named automata.

Class Constructors

S.No.	Constructor & Description
1	RegexpQuery(Term term) Constructs a query for terms matching term.
2	RegexpQuery(Term term, int flags) Constructs a query for terms matching term.
3	RegexpQuery(Term term, int flags, int determinizeWorkLimit) Constructs a query for terms matching term.
4	RegexpQuery(Term term, int syntaxFlags, int matchFlags, int determinizeWorkLimit) Constructs a query for terms matching term.
5	RegexpQuery(Term term, int syntaxFlags, int matchFlags, AutomatonProvider provider, int determinizeWorkLimit, MultiTermQuery.RewriteMethod rewriteMethod) Constructs a query for terms matching term.
6	RegexpQuery(Term term, int syntaxFlags, int matchFlags, AutomatonProvider provider, int determinizeWorkLimit, MultiTermQuery.RewriteMethod rewriteMethod, boolean doDeterminization) Constructs a query for terms matching term.
7	RegexpQuery(Term term, int syntaxFlags, AutomatonProvider provider, int determinizeWorkLimit) Constructs a query for terms matching term.

Class Methods

S.No.	Method & Description
1	Term getRegexp() Returns the regexp of this query wrapped in a Term.
2	String toString(String field) Prints a user-readable version of this query.

Methods Inherited

This class inherits methods from the following classes −

• org.apache.lucene.search.AutomatonQuery
• org.apache.lucene.search.MultiTermQuery
• org.apache.lucene.search.Query
• java.lang.Object

Usage of RegexpQuery

private void searchUsingRegexpQuery(String searchQuery) 
   throws IOException, ParseException { 
   searcher = new Searcher(indexDir); 
   long startTime = System.currentTimeMillis(); 

   //create a term to search file name 
   Term term = new Term(LuceneConstants.FILE_NAME, searchQuery); 
   //create the term query object 
   Query query = new RegexpQuery(term); 
   //do the search 
   TopDocs hits = searcher.search(query); 
   long endTime = System.currentTimeMillis(); 

   System.out.println(hits.totalHits + 
      " documents found. Time :" + (endTime - startTime) + "ms"); 

   for(ScoreDoc scoreDoc : hits.scoreDocs) { 
      Document doc = searcher.getDocument(scoreDoc); 
      System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH)); 
   } 
} 

Example Application

To test search using BooleanQuery, let us create a test Lucene application.

LuceneConstants.java

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

package com.tutorialspoint.lucene;

public class LuceneConstants {
   public static final String CONTENTS = "contents";
   public static final String FILE_NAME = "filename";
   public static final String FILE_PATH = "filepath";
   public 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 library.

package com.tutorialspoint.lucene;

import java.io.IOException;
import java.nio.file.Paths;
import java.text.ParseException;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.QueryBuilder;

public class Searcher {

   IndexSearcher indexSearcher;
   QueryBuilder queryBuilder;
   Query query;

   public Searcher(String indexDirectoryPath) 
      throws IOException {
      DirectoryReader indexDirectory = DirectoryReader.open(FSDirectory.open(Paths.get(indexDirectoryPath)));
      indexSearcher = new IndexSearcher(indexDirectory);
      StandardAnalyzer analyzer = new StandardAnalyzer();
      queryBuilder = new QueryBuilder(analyzer);
   }

   public TopDocs search( String searchQuery) 
      throws IOException, ParseException {
      query = queryBuilder.createPhraseQuery(LuceneConstants.CONTENTS, searchQuery);
      return indexSearcher.search(query, LuceneConstants.MAX_SEARCH);
   }

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

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

LuceneTester.java

This class is used to test the searching capability of the Lucene library.

package com.tutorialspoint.lucene;

import java.io.IOException;
import java.text.ParseException;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.search.RegexpQuery;

public class LuceneTester {
	
   String indexDir = "D:\\Lucene\\Index";
   String dataDir = "D:\\Lucene\\Data";
   Searcher searcher;

   public static void main(String[] args) {
      LuceneTester tester;
      try {
         tester = new LuceneTester();
         tester.searchUsingRegexpQuery("record1*.txt");
      } catch (IOException e) {
         e.printStackTrace();
      } catch (ParseException e) {
         e.printStackTrace();
      }
   }

   private void searchUsingRegexpQuery(String searchQuery) 
      throws IOException, ParseException { 
      searcher = new Searcher(indexDir); 
      long startTime = System.currentTimeMillis(); 

      //create a term to search file name 
      Term term = new Term(LuceneConstants.FILE_NAME, searchQuery); 
      //create the term query object 
      Query query = new RegexpQuery(term); 
      //do the search 
      TopDocs hits = searcher.search(query); 
      long endTime = System.currentTimeMillis(); 

      System.out.println(hits.totalHits + 
         " documents found. Time :" + (endTime - startTime) + "ms"); 

      for(ScoreDoc scoreDoc : hits.scoreDocs) { 
         Document doc = searcher.getDocument(scoreDoc); 
         System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH)); 
      }
   } 
}

Data & Index Directory Creation

I've used 10 text files from record1.txt to record10.txt containing names and other details of the students and put them in the directory D:\Lucene\Data. Test Data. An index directory path should be created as D:\Lucene\Index. After running the indexing program in the chapter Lucene - Indexing Process, you can see the list 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 proceed by compiling and running your program. To do this, keep the LuceneTester.Java file tab active and use either the Run option available in the Eclipse IDE or use Ctrl + F11 to compile and run your LuceneTester application. If your application runs successfully, it will print the following message in Eclipse IDE's console −

Output

1 hits documents found. Time :53ms
File: D:\lucene\Data\record1.txt