Lucene - MatchNoDocsQuery

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MatchNoDocsQuery class as the name suggests, matches no documents.

Class Declaration

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

public class MatchNoDocsQuery
   extends Query

Class Constructors

S.No.	Constructor & Description
1	MatchNoDocsQuery() Default Constructor
2	MatchNoDocsQuery(String reason) Provides a reason explaining why this query was used.

Class Methods

S.No.	Method & Description
1	Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) Expert: Constructs an appropriate Weight implementation for this query.
2	boolean equals(Object obj) Override and implement query instance equivalence properly in a subclass.
3	int hashCode() Override and implement query hash code properly in a subclass.
4	String toString(String field) Prints a query to a string, with field assumed to be the default field and omitted.
5	void visit(QueryVisitor visitor) Recurse through the query tree, visiting any child queries.

Methods Inherited

This class inherits methods from the following classes −

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

Usage of MatchNoDocsQuery

private void searchUsingMatchNoDocsQuery()
   throws IOException, ParseException {
   searcher = new Searcher(indexDir);
   long startTime = System.currentTimeMillis();
      
   //create the term query object
   Query query = new MatchNoDocsQuery();
   //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.print("Score: "+ scoreDoc.score + " ");
      System.out.println("Doc ID: " + scoreDoc.doc);
   }
}

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.search.MatchNoDocsQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;

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.searchUsingMatchNoDocsQuery();
      } catch (IOException e) {
         e.printStackTrace();
      } catch (ParseException e) {
         e.printStackTrace();
      }
   }
   private void searchUsingMatchNoDocsQuery()
      throws IOException, ParseException {
      searcher = new Searcher(indexDir);
      long startTime = System.currentTimeMillis();
      
      //create the term query object
      Query query = new MatchNoDocsQuery();
      //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.print("Score: "+ scoreDoc.score + " ");
         System.out.println("Doc ID: " + scoreDoc.doc);
      }
   }
}

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

0 hits documents found. Time :9ms