1 package org.apache.lucene.search;
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
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14 * distributed under the License is distributed on an "AS IS" BASIS,
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16 * See the License for the specific language governing permissions and
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20 import java.io.IOException;
22 import org.apache.lucene.index.IndexReader;
23 import org.apache.lucene.util.DocIdBitSet;
26 * Abstract base class for restricting which documents may
27 * be returned during searching.
29 public abstract class Filter implements java.io.Serializable {
32 * Creates a {@link DocIdSet} enumerating the documents that should be
33 * permitted in search results. <b>NOTE:</b> null can be
34 * returned if no documents are accepted by this Filter.
36 * Note: This method will be called once per segment in
37 * the index during searching. The returned {@link DocIdSet}
38 * must refer to document IDs for that segment, not for
39 * the top-level reader.
41 * @param reader a {@link IndexReader} instance opened on the index currently
42 * searched on. Note, it is likely that the provided reader does not
43 * represent the whole underlying index i.e. if the index has more than
44 * one segment the given reader only represents a single segment.
46 * @return a DocIdSet that provides the documents which should be permitted or
47 * prohibited in search results. <b>NOTE:</b> null can be returned if
48 * no documents will be accepted by this Filter.
52 public abstract DocIdSet getDocIdSet(IndexReader reader) throws IOException;