/*
* 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.
*/
using System;
using System.Collections;
using System.Collections.Generic;
using Lucene.Net.Support;
using IndexReader = Lucene.Net.Index.IndexReader;
using OpenBitSetDISI = Lucene.Net.Util.OpenBitSetDISI;
using Lucene.Net.Util;
namespace Lucene.Net.Search
{
/// Wraps another filter's result and caches it. The purpose is to allow
/// filters to simply filter, and then wrap with this class to add caching.
///
[Serializable]
public class CachingWrapperFilter:Filter
{
protected internal Filter filter;
///
/// Expert: Specifies how new deletions against a reopened
/// reader should be handled.
///
/// The default is IGNORE, which means the cache entry
/// will be re-used for a given segment, even when that
/// segment has been reopened due to changes in deletions.
/// This is a big performance gain, especially with
/// near-real-timer readers, since you don't hit a cache
/// miss on every reopened reader for prior segments.
///
/// However, in some cases this can cause invalid query
/// results, allowing deleted documents to be returned.
/// This only happens if the main query does not rule out
/// deleted documents on its own, such as a toplevel
/// ConstantScoreQuery. To fix this, use RECACHE to
/// re-create the cached filter (at a higher per-reopen
/// cost, but at faster subsequent search performance), or
/// use DYNAMIC to dynamically intersect deleted docs (fast
/// reopen time but some hit to search performance).
///
public enum DeletesMode { IGNORE, RECACHE, DYNAMIC }
internal FilterCache cache;
[Serializable]
abstract internal class FilterCache where T : class
{
/*
* A transient Filter cache (package private because of test)
*/
// NOTE: not final so that we can dynamically re-init
// after de-serialize
volatile IDictionary cache;
private DeletesMode deletesMode;
public FilterCache(DeletesMode deletesMode)
{
this.deletesMode = deletesMode;
}
public T Get(IndexReader reader, object coreKey, object delCoreKey)
{
lock (this)
{
T value;
if (cache == null)
{
cache = new WeakDictionary();
}
if (deletesMode == DeletesMode.IGNORE)
{
// key on core
value = cache[coreKey];
}
else if (deletesMode == DeletesMode.RECACHE)
{
// key on deletes, if any, else core
value = cache[delCoreKey];
}
else
{
System.Diagnostics.Debug.Assert(deletesMode == DeletesMode.DYNAMIC);
// first try for exact match
value = cache[delCoreKey];
if (value == null)
{
// now for core match, but dynamically AND NOT
// deletions
value = cache[coreKey];
if (value != null && reader.HasDeletions)
{
value = MergeDeletes(reader, value);
}
}
}
return value;
}
}
protected abstract T MergeDeletes(IndexReader reader, T value);
public void Put(object coreKey, object delCoreKey, T value)
{
lock (this)
{
if (deletesMode == DeletesMode.IGNORE)
{
cache[coreKey] = value;
}
else if (deletesMode == DeletesMode.RECACHE)
{
cache[delCoreKey] = value;
}
else
{
cache[coreKey] = value;
cache[delCoreKey] = value;
}
}
}
}
///
/// New deletes are ignored by default, which gives higher
/// cache hit rate on reopened readers. Most of the time
/// this is safe, because the filter will be AND'd with a
/// Query that fully enforces deletions. If instead you
/// need this filter to always enforce deletions, pass
/// either or
/// .
///
/// Filter to cache results of
///
public CachingWrapperFilter(Filter filter) : this(filter, DeletesMode.IGNORE)
{
}
///
/// Expert: by default, the cached filter will be shared
/// across reopened segments that only had changes to their
/// deletions.
///
/// Filter to cache results of
/// See
///
public CachingWrapperFilter(Filter filter, DeletesMode deletesMode)
{
this.filter = filter;
cache = new AnonymousFilterCache(deletesMode);
//cache = new FilterCache(deletesMode)
// {
// public Object mergeDeletes(final IndexReader r, final Object docIdSet) {
// return new FilteredDocIdSet((DocIdSet) docIdSet) {
// protected boolean match(int docID) {
// return !r.isDeleted(docID);
// }
// };
// }
//};
}
class AnonymousFilterCache : FilterCache
{
class AnonymousFilteredDocIdSet : FilteredDocIdSet
{
IndexReader r;
public AnonymousFilteredDocIdSet(DocIdSet innerSet, IndexReader r) : base(innerSet)
{
this.r = r;
}
public override bool Match(int docid)
{
return !r.IsDeleted(docid);
}
}
public AnonymousFilterCache(DeletesMode deletesMode) : base(deletesMode)
{ }
protected override DocIdSet MergeDeletes(IndexReader reader, DocIdSet docIdSet)
{
return new AnonymousFilteredDocIdSet(docIdSet, reader);
}
}
/// Provide the DocIdSet to be cached, using the DocIdSet provided
/// by the wrapped Filter.
/// This implementation returns the given DocIdSet.
///
protected internal virtual DocIdSet DocIdSetToCache(DocIdSet docIdSet, IndexReader reader)
{
if (docIdSet == null)
{
// this is better than returning null, as the nonnull result can be cached
return DocIdSet.EMPTY_DOCIDSET;
}
else if (docIdSet.IsCacheable) {
return docIdSet;
}
else
{
DocIdSetIterator it = docIdSet.Iterator();
// null is allowed to be returned by iterator(),
// in this case we wrap with the empty set,
// which is cacheable.
return (it == null) ? DocIdSet.EMPTY_DOCIDSET : new OpenBitSetDISI(it, reader.MaxDoc);
}
}
// for testing
public int hitCount, missCount;
public override DocIdSet GetDocIdSet(IndexReader reader)
{
object coreKey = reader.FieldCacheKey;
object delCoreKey = reader.HasDeletions ? reader.DeletesCacheKey : coreKey;
DocIdSet docIdSet = cache.Get(reader, coreKey, delCoreKey);
if (docIdSet != null)
{
hitCount++;
return docIdSet;
}
missCount++;
// cache miss
docIdSet = DocIdSetToCache(filter.GetDocIdSet(reader), reader);
if (docIdSet != null)
{
cache.Put(coreKey, delCoreKey, docIdSet);
}
return docIdSet;
}
public override System.String ToString()
{
return "CachingWrapperFilter(" + filter + ")";
}
public override bool Equals(System.Object o)
{
if (!(o is CachingWrapperFilter))
return false;
return this.filter.Equals(((CachingWrapperFilter) o).filter);
}
public override int GetHashCode()
{
return filter.GetHashCode() ^ 0x1117BF25;
}
}
}