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;
/**
* Abstract decorator class for a DocIdSet implementation
* that provides on-demand filtering/validation
* mechanism on a given DocIdSet.
*
* <p/>
*
* Technically, this same functionality could be achieved
* with ChainedFilter (under contrib/misc), however the
* benefit of this class is it never materializes the full
* bitset for the filter. Instead, the {@link #match}
* method is invoked on-demand, per docID visited during
* searching. If you know few docIDs will be visited, and
* the logic behind {@link #match} is relatively costly,
* this may be a better way to filter than ChainedFilter.
*
* @see DocIdSet
*/
public abstract class FilteredDocIdSet extends DocIdSet {
private final DocIdSet _innerSet;
/**
* Constructor.
* @param innerSet Underlying DocIdSet
*/
public FilteredDocIdSet(DocIdSet innerSet) {
_innerSet = innerSet;
}
/** This DocIdSet implementation is cacheable if the inner set is cacheable. */
@Override
public boolean isCacheable() {
return _innerSet.isCacheable();
}
/**
* Validation method to determine whether a docid should be in the result set.
* @param docid docid to be tested
* @return true if input docid should be in the result set, false otherwise.
*/
protected abstract boolean match(int docid) throws IOException;
/**
* Implementation of the contract to build a DocIdSetIterator.
* @see DocIdSetIterator
* @see FilteredDocIdSetIterator
*/
@Override
public DocIdSetIterator iterator() throws IOException {
return new FilteredDocIdSetIterator(_innerSet.iterator()) {
@Override
protected boolean match(int docid) throws IOException {
return FilteredDocIdSet.this.match(docid);
}
};
}
}