/*
* 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.solr.search;
import org.apache.lucene.search.IndexSearcher;
/** The PostFilter interface provides a mechanism to further filter documents
* after they have already gone through the main query and other filters.
* This is appropriate for filters with a very high cost.
* <p>
* The filtering mechanism used is a {@link DelegatingCollector}
* that allows the filter to not call the delegate for certain documents,
* thus effectively filtering them out. This also avoids the normal
* filter advancing mechanism which asks for the first acceptable document on
* or after the target (which is undesirable for expensive filters).
* This collector interface also enables better performance when an external system
* must be consulted, since document ids may be buffered and batched into
* a single request to the external system.
* <p>
* Implementations of this interface must also be a Query.
* If an implementation can only support the collector method of
* filtering through getFilterCollector, then ExtendedQuery.getCached()
* should always return false, and ExtendedQuery.getCost() should
* return no less than 100.
*
* @see ExtendedQueryBase
*/
public interface PostFilter extends ExtendedQuery {
/** Returns a DelegatingCollector to be run after the main query and all of its filters, but before any sorting or grouping collectors */
public DelegatingCollector getFilterCollector(IndexSearcher searcher);
}