| 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.IOException; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.WeakHashMap; |
| |
| import org.apache.lucene.index.AtomicReader; |
| import org.apache.lucene.index.AtomicReaderContext; |
| import org.apache.lucene.util.Bits; |
| import org.apache.lucene.util.RamUsageEstimator; |
| import org.apache.lucene.util.WAH8DocIdSet; |
| |
| /** |
| * Wraps another {@link Filter}'s result and caches it. The purpose is to allow |
| * filters to simply filter, and then wrap with this class |
| * to add caching. |
| */ |
| public class CachingWrapperFilter extends Filter { |
| private final Filter filter; |
| private final Map<Object,DocIdSet> cache = Collections.synchronizedMap(new WeakHashMap<Object,DocIdSet>()); |
| |
| /** Wraps another filter's result and caches it. |
| * @param filter Filter to cache results of |
| */ |
| public CachingWrapperFilter(Filter filter) { |
| this.filter = filter; |
| } |
| |
| /** |
| * Gets the contained filter. |
| * @return the contained filter. |
| */ |
| public Filter getFilter() { |
| return filter; |
| } |
| |
| /** |
| * Provide the DocIdSet to be cached, using the DocIdSet provided |
| * by the wrapped Filter. <p>This implementation returns the given {@link DocIdSet}, |
| * if {@link DocIdSet#isCacheable} returns <code>true</code>, else it calls |
| * {@link #cacheImpl(DocIdSetIterator,AtomicReader)} |
| * <p>Note: This method returns {@linkplain #EMPTY_DOCIDSET} if the given docIdSet |
| * is <code>null</code> or if {@link DocIdSet#iterator()} return <code>null</code>. The empty |
| * instance is use as a placeholder in the cache instead of the <code>null</code> value. |
| */ |
| protected DocIdSet docIdSetToCache(DocIdSet docIdSet, AtomicReader reader) throws IOException { |
| if (docIdSet == null) { |
| // this is better than returning null, as the nonnull result can be cached |
| return EMPTY_DOCIDSET; |
| } else if (docIdSet.isCacheable()) { |
| return docIdSet; |
| } else { |
| final DocIdSetIterator it = docIdSet.iterator(); |
| // null is allowed to be returned by iterator(), |
| // in this case we wrap with the sentinel set, |
| // which is cacheable. |
| if (it == null) { |
| return EMPTY_DOCIDSET; |
| } else { |
| return cacheImpl(it, reader); |
| } |
| } |
| } |
| |
| /** |
| * Default cache implementation: uses {@link WAH8DocIdSet}. |
| */ |
| protected DocIdSet cacheImpl(DocIdSetIterator iterator, AtomicReader reader) throws IOException { |
| WAH8DocIdSet.Builder builder = new WAH8DocIdSet.Builder(); |
| builder.add(iterator); |
| return builder.build(); |
| } |
| |
| // for testing |
| int hitCount, missCount; |
| |
| @Override |
| public DocIdSet getDocIdSet(AtomicReaderContext context, final Bits acceptDocs) throws IOException { |
| final AtomicReader reader = context.reader(); |
| final Object key = reader.getCoreCacheKey(); |
| |
| DocIdSet docIdSet = cache.get(key); |
| if (docIdSet != null) { |
| hitCount++; |
| } else { |
| missCount++; |
| docIdSet = docIdSetToCache(filter.getDocIdSet(context, null), reader); |
| assert docIdSet.isCacheable(); |
| cache.put(key, docIdSet); |
| } |
| |
| return docIdSet == EMPTY_DOCIDSET ? null : BitsFilteredDocIdSet.wrap(docIdSet, acceptDocs); |
| } |
| |
| @Override |
| public String toString() { |
| return getClass().getSimpleName() + "("+filter+")"; |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (o == null || !getClass().equals(o.getClass())) return false; |
| final CachingWrapperFilter other = (CachingWrapperFilter) o; |
| return this.filter.equals(other.filter); |
| } |
| |
| @Override |
| public int hashCode() { |
| return (filter.hashCode() ^ getClass().hashCode()); |
| } |
| |
| /** An empty {@code DocIdSet} instance */ |
| protected static final DocIdSet EMPTY_DOCIDSET = new DocIdSet() { |
| |
| @Override |
| public DocIdSetIterator iterator() { |
| return DocIdSetIterator.empty(); |
| } |
| |
| @Override |
| public boolean isCacheable() { |
| return true; |
| } |
| |
| // we explicitly provide no random access, as this filter is 100% sparse and iterator exits faster |
| @Override |
| public Bits bits() { |
| return null; |
| } |
| }; |
| |
| /** Returns total byte size used by cached filters. */ |
| public long sizeInBytes() { |
| |
| // Sync only to pull the current set of values: |
| List<DocIdSet> docIdSets; |
| synchronized(cache) { |
| docIdSets = new ArrayList<DocIdSet>(cache.values()); |
| } |
| |
| long total = 0; |
| for(DocIdSet dis : docIdSets) { |
| total += RamUsageEstimator.sizeOf(dis); |
| } |
| |
| return total; |
| } |
| } |