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/*
* COPIED FROM APACHE LUCENE 4.7.2
*
* Git URL: [email protected]:apache/lucene.git, tag: releases/lucene-solr/4.7.2, path: lucene/core/src/java
*
* (see https://issues.apache.org/jira/browse/OAK-10786 for details)
*/
package org.apache.lucene.search;
/*
* 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.
*/
import java.io.Closeable;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/** Tracks live field values across NRT reader reopens.
* This holds a map for all updated ids since
* the last reader reopen. Once the NRT reader is reopened,
* it prunes the map. This means you must reopen your NRT
* reader periodically otherwise the RAM consumption of
* this class will grow unbounded!
*
* NOTE: you must ensure the same id is never updated at
* the same time by two threads, because in this case you
* cannot in general know which thread "won". */
public abstract class LiveFieldValues implements ReferenceManager.RefreshListener, Closeable {
private volatile Map current = new ConcurrentHashMap();
private volatile Map old = new ConcurrentHashMap();
private final ReferenceManager mgr;
private final T missingValue;
public LiveFieldValues(ReferenceManager mgr, T missingValue) {
this.missingValue = missingValue;
this.mgr = mgr;
mgr.addListener(this);
}
@Override
public void close() {
mgr.removeListener(this);
}
@Override
public void beforeRefresh() throws IOException {
old = current;
// Start sending all updates after this point to the new
// map. While reopen is running, any lookup will first
// try this new map, then fallback to old, then to the
// current searcher:
current = new ConcurrentHashMap();
}
@Override
public void afterRefresh(boolean didRefresh) throws IOException {
// Now drop all the old values because they are now
// visible via the searcher that was just opened; if
// didRefresh is false, it's possible old has some
// entries in it, which is fine: it means they were
// actually already included in the previously opened
// reader. So we can safely clear old here:
old = new ConcurrentHashMap();
}
/** Call this after you've successfully added a document
* to the index, to record what value you just set the
* field to. */
public void add(String id, T value) {
current.put(id, value);
}
/** Call this after you've successfully deleted a document
* from the index. */
public void delete(String id) {
current.put(id, missingValue);
}
/** Returns the [approximate] number of id/value pairs
* buffered in RAM. */
public int size() {
return current.size() + old.size();
}
/** Returns the current value for this id, or null if the
* id isn't in the index or was deleted. */
public T get(String id) throws IOException {
// First try to get the "live" value:
T value = current.get(id);
if (value == missingValue) {
// Deleted but the deletion is not yet reflected in
// the reader:
return null;
} else if (value != null) {
return value;
} else {
value = old.get(id);
if (value == missingValue) {
// Deleted but the deletion is not yet reflected in
// the reader:
return null;
} else if (value != null) {
return value;
} else {
// It either does not exist in the index, or, it was
// already flushed & NRT reader was opened on the
// segment, so fallback to current searcher:
S s = mgr.acquire();
try {
return lookupFromSearcher(s, id);
} finally {
mgr.release(s);
}
}
}
}
/** This is called when the id/value was already flushed & opened
* in an NRT IndexSearcher. You must implement this to
* go look up the value (eg, via doc values, field cache,
* stored fields, etc.). */
protected abstract T lookupFromSearcher(S s, String id) throws IOException;
}