Lucene - Updating index for an existing file. How to delete a documents from the index?

LuceneExample.java

/* LuceneExample.java */

import java.io.File;
import java.io.FileReader;
import java.io.Reader;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.IndexWriter.MaxFieldLength;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.store.SimpleFSDirectory;
import org.apache.lucene.util.Version;

public class LuceneExample {

	public static final String files = "C:/TestLucene/files";
	public static final String index = "C:/TestLucene/index";

	public static void createIndex() {

		System.out.println("Creating index....");

		Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30);
		try {
			// Store the index in file

			Directory directory = new SimpleFSDirectory(new File(index));
			IndexWriter iwriter = new IndexWriter(directory, analyzer, true,
					MaxFieldLength.UNLIMITED);
			File dir = new File(files);

			File[] files = dir.listFiles();
			
			int i = 1;

			for (File file : files) {
				System.out.println(file.getPath());
				Document doc = new Document();
				
				doc.add(new Field("id",""+i,Field.Store.YES,Field.Index.ANALYZED));

				doc.add(new Field("path", file.getPath(), Field.Store.YES,
						Field.Index.ANALYZED));

				Reader reader = new FileReader(file.getCanonicalPath());

				doc.add(new Field("contents", reader));
				iwriter.addDocument(doc);
				
				i++;
			}

			iwriter.optimize();
			iwriter.close();
		} catch (Exception e) {

			e.printStackTrace();
		}

	}

	public static void searchIndex(String searchString) {

		System.out.println("Searching.... '" + searchString + "'");

		try {
			IndexReader reader = IndexReader.open(FSDirectory.open(new File(
					index)), true);
			IndexSearcher searcher = new IndexSearcher(reader);

			Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30);// construct our usual analyzer

			QueryParser qp = new QueryParser(Version.LUCENE_30, "contents",
					analyzer);
			Query query = qp.parse(searchString); // parse the query and construct the Query object

			TopDocs hits = searcher.search(query, 100); // run the query

			if (hits.totalHits == 0) {
				System.out.println("No data found.");
			} else {
				for (int i = 0; i < hits.totalHits; i++) {
					Document doc = searcher.doc(hits.scoreDocs[i].doc); // get the next document
					String id = doc.get("id"); // get its id field
					String url = doc.get("path"); // get its path field
					System.out.println("Found in :: "+ id +" "+ url);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public static void updateIndex(File newFile) {

		System.out.println("Updating index....");

		Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30);
		try {
			// Store the index in file

			Directory directory = new SimpleFSDirectory(new File(index));
			IndexWriter iwriter = new IndexWriter(directory, analyzer, false,
					MaxFieldLength.UNLIMITED);

			System.out.println(newFile.getPath());
			Document doc = new Document();
			
			//get max id
			IndexReader iReader = IndexReader.open(FSDirectory.open(new File(index)), true);
			int i = iReader.maxDoc();
			i++;
			
			doc.add(new Field("id",""+i,Field.Store.YES,Field.Index.ANALYZED));

			doc.add(new Field("path", newFile.getPath(), Field.Store.YES,
					Field.Index.ANALYZED));

			Reader reader = new FileReader(newFile.getCanonicalPath());

			doc.add(new Field("contents", reader));
			iwriter.addDocument(doc);

			iwriter.optimize();
			iwriter.close();
		} catch (Exception e) {

			e.printStackTrace();
		}

	}
	
	public static void deleteIndex(String id) {
		
		System.out.println("Deleting index...."+id);
		
		try {
			Term term = new Term("id", id);
			
			Directory directory = FSDirectory.open(new File(index));
			
			IndexReader indexReader = IndexReader.open(directory, false);
			indexReader.deleteDocuments(term);
			
			indexReader.flush();
			indexReader.close();
			
		}
		catch (Exception e) {
			e.printStackTrace();
		}
	}


	public static void main(String[] args) {

		createIndex();
		searchIndex("Object");
		
		updateIndex(new File("C:/TestLucene/newFiles/PHP.txt"));
		searchIndex("Object");
		
		deleteIndex("2");//id to be deleted
		searchIndex("Object");
	}

}

issue with your updateIndex method you used add document method not update document method of index writer class
...

Hello. I use Lucene .Net version 2.9.4.1 in ASP.Net MVC 5. But I can't delete document from indexer. I Use WhitespaceAnalyzer for indexer. For add field to lucene document I use this code

var luceneDoc = new Document();
var fieldId = new NumericField("Id", Field.Store.YES, true);
fieldId.SetIntValue(2211);
luceneDoc.Add(fieldId);

Than I add document to indexer

private readonly Analyzer _whitespaceAnalyzer=new WhitespaceAnalyzer();
using (FSDirectory indexDirectory = FSDirectory.Open(new DirectoryInfo(indexLocationAbsolute)))
using (IndexWriter writer = new IndexWriter(indexDirectory, _whitespaceAnalyzer, IndexWriter.MaxFieldLength.UNLIMITED))
{
writer.AddDocument(document);
writer.Flush(false, true, true);
}

It's work good. I can search this document by "Id" for this query:
var query = NumericRangeQuery.NewIntRange("Id", id, id, true, true);

But I cant delete this document from indexer.
private readonly Analyzer _whitespaceAnalyzer=new WhitespaceAnalyzer();
using (FSDirectory indexDirectory = FSDirectory.Open(new DirectoryInfo(indexLocationAbsolute)))
using (IndexWriter writer = new IndexWriter(indexDirectory, _whitespaceAnalyzer, IndexWriter.MaxFieldLength.UNLIMITED))
{
var query = NumericRangeQuery.NewIntRange("Id", id, id, true, true);
writer.DeleteDocuments(query);
writer.Flush(false, true, true);
}

What a problem? Thanks!