org.elasticsearch.common.lucene.SegmentReaderUtils Maven / Gradle / Ivy
/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.common.lucene;
import org.apache.lucene.index.AtomicReader;
import org.apache.lucene.index.FilterAtomicReader;
import org.apache.lucene.index.SegmentReader;
import org.elasticsearch.ElasticsearchIllegalStateException;
import org.elasticsearch.common.Nullable;
import java.lang.reflect.Field;
public class SegmentReaderUtils {
private static final Field FILTER_ATOMIC_READER_IN;
static {
Field in = null;
try { // and another one bites the dust...
in = FilterAtomicReader.class.getDeclaredField("in");
in.setAccessible(true);
} catch (NoSuchFieldException e) {
assert false : "Failed to get field: " + e.getMessage();
}
FILTER_ATOMIC_READER_IN = in;
}
/**
* Tries to extract a segment reader from the given index reader.
* If no SegmentReader can be extracted an {@link org.elasticsearch.ElasticsearchIllegalStateException} is thrown.
*/
@Nullable
public static SegmentReader segmentReader(AtomicReader reader) {
return internalSegmentReader(reader, true);
}
/**
* Tries to extract a segment reader from the given index reader and returns it, otherwise null
* is returned
*/
@Nullable
public static SegmentReader segmentReaderOrNull(AtomicReader reader) {
return internalSegmentReader(reader, false);
}
public static boolean registerCoreListener(AtomicReader reader, SegmentReader.CoreClosedListener listener) {
SegmentReader segReader = SegmentReaderUtils.segmentReaderOrNull(reader);
if (segReader != null) {
segReader.addCoreClosedListener(listener);
return true;
}
return false;
}
private static SegmentReader internalSegmentReader(AtomicReader reader, boolean fail) {
if (reader == null) {
return null;
}
if (reader instanceof SegmentReader) {
return (SegmentReader) reader;
} else if (reader instanceof FilterAtomicReader) {
final FilterAtomicReader fReader = (FilterAtomicReader) reader;
try {
return FILTER_ATOMIC_READER_IN == null ? null :
segmentReader((AtomicReader) FILTER_ATOMIC_READER_IN.get(fReader));
} catch (IllegalAccessException e) {
}
}
if (fail) {
// hard fail - we can't get a SegmentReader
throw new ElasticsearchIllegalStateException("Can not extract segment reader from given index reader [" + reader + "]");
}
return null;
}
}