content: /**
   * 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 it's filters, but before any sorting or grouping collectors */
    public DelegatingCollector getFilterCollector(IndexSearcher searcher);
  }
  