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From "Erdman, Jon" <Jon.Erd...@solers.com>
Subject Using FSDirectory after a write
Date Tue, 21 Jun 2005 14:29:10 GMT
I am working on an application that requires indexing of a relatively
constant stream of data.  All of the documentation that I have read
seems to indicate that writing to the index will not affect searching,
but I have run into some problems using FSDirectory in this case.  

 

It looks like FSDirectory only locks the database for long enough to
read the segment information and create input streams to the files.  It
does not try to read the input streams until an actual search occurs,
after the commit.lock has been released.  If the index is has been
modified since then the search will result in an IOException as it tries
to read the input stream to a file that no longer exists.  I have
included a full sample class below that will reproduce this error.

 

Our application is currently creating a new FSDirectory instance for
each search.  This is causing a bottleneck when retrieving the lock and
loading the segments due to the large number of searches we receive.  Is
there anyway to reuse a FSDirectory in a safe way?  We have considered
using RAMDirectory instead but our index can grow too large to store in
memory.

 

Thanks,

Jon

 

 

package search;

 

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.IndexWriter;

import org.apache.lucene.queryParser.ParseException;

import org.apache.lucene.queryParser.QueryParser;

import org.apache.lucene.search.Hits;

import org.apache.lucene.search.IndexSearcher;

import org.apache.lucene.search.Query;

import org.apache.lucene.store.Directory;

import org.apache.lucene.store.FSDirectory;

import java.io.IOException;

 

public class LuceneLockTest {

 

    public static final String INDEX_DIR =
"C:\\testIndex\\lucene-index";

 

    public LuceneLockTest() {

    }

 

    public static void main(String[] args) throws Exception {

        Directory directory = null;

        Directory ramDir = null;

        try {

            LuceneLockTest test = new LuceneLockTest();

            //initial index

            test.indexArticle("test 1", true);

            directory = test.getFSDirectory(INDEX_DIR, false);

            IndexSearcher is = new IndexSearcher(directory);

            System.out.println("Search 1: ");

            //initial search succeeds

            test.search ("test", is);

            test.indexArticle("test 2", false);

            System.out.println("Search 2: ");

            //search after second index fails with old searcher

            test.search("test", is);

        } finally {

            if (directory != null) {

                directory.close();

            }

        }

    }

 

    private Directory getFSDirectory(String indexDirectory, boolean
create) throws IOException {

        return FSDirectory.getDirectory(indexDirectory, create);

    }

 

    private Directory getRAMDirectory(Directory dir) throws IOException
{

        return new RAMDirectory(dir);

    }

 

    public void search(String searchCriteria, IndexSearcher is) throws
IOException, ParseException {

        Analyzer analyzer = new StandardAnalyzer();

        QueryParser parser = new QueryParser("title", analyzer);

        Query query = parser.parse(searchCriteria);

        Hits hits = is.search(query);

        for (int i = 0; i < hits.length(); i++) {

            Document doc = hits.doc(i);

            System.out.println(doc.getField("title"));

        }

        is.close();

    }

 

    public void indexArticle(String title, boolean create)

            throws Exception {

        Document document = createDocument(title);

        indexDocument(document, create);

    }

 

    private void indexDocument(Document document, boolean create) throws
Exception {

        IndexWriter writer = null;

        Directory directory = null;

        try {

            directory = getFSDirectory(INDEX_DIR, false);

            Analyzer analyzer = new StandardAnalyzer();

            writer = new IndexWriter(directory, analyzer, create);

            writer.addDocument(document);

            //writer.optimize();

        } finally {

            writer.close();

            directory.close();

        }

    }

 

    private Document createDocument(String title) {

        Document document = new Document();

        document.add(Field.Text("title", title));

        return document;

    }

}


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