org.apache.lucene.index.ReaderManager.java Source code

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Here is the source code for org.apache.lucene.index.ReaderManager.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.index;

import java.io.IOException;

import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.ReferenceManager;
import org.apache.lucene.search.SearcherManager;
import org.apache.lucene.store.Directory;

/**
 * Utility class to safely share {@link DirectoryReader} instances across
 * multiple threads, while periodically reopening. This class ensures each
 * reader is closed only once all threads have finished using it.
 * 
 * @see SearcherManager
 * 
 * @lucene.experimental
 */
public final class ReaderManager extends ReferenceManager<DirectoryReader> {

    /**
     * Creates and returns a new ReaderManager from the given
     * {@link IndexWriter}.
     * 
     * @param writer
     *          the IndexWriter to open the IndexReader from.
     * 
     * @throws IOException If there is a low-level I/O error
     */
    public ReaderManager(IndexWriter writer) throws IOException {
        this(writer, true, false);
    }

    /**
     * Expert: creates and returns a new ReaderManager from the given
     * {@link IndexWriter}, controlling whether past deletions should be applied.
     * 
     * @param writer
     *          the IndexWriter to open the IndexReader from.
     * @param applyAllDeletes
     *          If <code>true</code>, all buffered deletes will be applied (made
     *          visible) in the {@link IndexSearcher} / {@link DirectoryReader}.
     *          If <code>false</code>, the deletes may or may not be applied, but
     *          remain buffered (in IndexWriter) so that they will be applied in
     *          the future. Applying deletes can be costly, so if your app can
     *          tolerate deleted documents being returned you might gain some
     *          performance by passing <code>false</code>. See
     *          {@link DirectoryReader#openIfChanged(DirectoryReader, IndexWriter, boolean)}.
     * @param writeAllDeletes
     *          If <code>true</code>, new deletes will be forcefully written to index files.
     * 
     * @throws IOException If there is a low-level I/O error
     */
    public ReaderManager(IndexWriter writer, boolean applyAllDeletes, boolean writeAllDeletes) throws IOException {
        current = DirectoryReader.open(writer, applyAllDeletes, writeAllDeletes);
    }

    /**
     * Creates and returns a new ReaderManager from the given {@link Directory}. 
     * @param dir the directory to open the DirectoryReader on.
     *        
     * @throws IOException If there is a low-level I/O error
     */
    public ReaderManager(Directory dir) throws IOException {
        current = DirectoryReader.open(dir);
    }

    /**
     * Creates and returns a new ReaderManager from the given
     * already-opened {@link DirectoryReader}, stealing
     * the incoming reference.
     *
     * @param reader the directoryReader to use for future reopens
     *        
     * @throws IOException If there is a low-level I/O error
     */
    public ReaderManager(DirectoryReader reader) throws IOException {
        current = reader;
    }

    @Override
    protected void decRef(DirectoryReader reference) throws IOException {
        reference.decRef();
    }

    @Override
    protected DirectoryReader refreshIfNeeded(DirectoryReader referenceToRefresh) throws IOException {
        return DirectoryReader.openIfChanged(referenceToRefresh);
    }

    @Override
    protected boolean tryIncRef(DirectoryReader reference) {
        return reference.tryIncRef();
    }

    @Override
    protected int getRefCount(DirectoryReader reference) {
        return reference.getRefCount();
    }

}