/*
* 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.codecs.bloom;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.SegmentWriteState;
/**
* Class used to create index-time {@link FuzzySet} appropriately configured for
* each field. Also called to right-size bitsets for serialization.
* @lucene.experimental
*/
public abstract class BloomFilterFactory {
/**
*
* @param state The content to be indexed
* @param info
* the field requiring a BloomFilter
* @return An appropriately sized set or null if no BloomFiltering required
*/
public abstract FuzzySet getSetForField(SegmentWriteState state, FieldInfo info);
/**
* Called when downsizing bitsets for serialization
*
* @param fieldInfo
* The field with sparse set bits
* @param initialSet
* The bits accumulated
* @return null or a hopefully more densely packed, smaller bitset
*/
public FuzzySet downsize(FieldInfo fieldInfo, FuzzySet initialSet) {
// Aim for a bitset size that would have 10% of bits set (so 90% of searches
// would fail-fast)
float targetMaxSaturation = 0.1f;
return initialSet.downsize(targetMaxSaturation);
}
/**
* Used to determine if the given filter has reached saturation and should be retired i.e. not saved any more
* @param bloomFilter The bloomFilter being tested
* @param fieldInfo The field with which this filter is associated
* @return true if the set has reached saturation and should be retired
*/
public abstract boolean isSaturated(FuzzySet bloomFilter, FieldInfo fieldInfo);
}