/*
* 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.search;
import java.io.IOException;
/**
* A policy defining which filters should be cached.
*
* Implementations of this class must be thread-safe.
*
* @see UsageTrackingQueryCachingPolicy
* @see LRUQueryCache
* @lucene.experimental
*/
// TODO: add APIs for integration with IndexWriter.IndexReaderWarmer
public interface QueryCachingPolicy {
/** A simple policy that caches all the provided filters on all segments. */
public static final QueryCachingPolicy ALWAYS_CACHE = new QueryCachingPolicy() {
@Override
public void onUse(Query query) {}
@Override
public boolean shouldCache(Query query) throws IOException {
return true;
}
};
/** Callback that is called every time that a cached filter is used.
* This is typically useful if the policy wants to track usage statistics
* in order to make decisions. */
void onUse(Query query);
/** Whether the given {@link Query} is worth caching.
* This method will be called by the {@link QueryCache} to know whether to
* cache. It will first attempt to load a {@link DocIdSet} from the cache.
* If it is not cached yet and this method returns <tt>true</tt> then a
* cache entry will be generated. Otherwise an uncached scorer will be
* returned. */
boolean shouldCache(Query query) throws IOException;
}