1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements.  See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License.  You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 
18 using System;
19 
20 using IndexReader = Lucene.Net.Index.IndexReader;
21 using DocIdBitSet = Lucene.Net.Util.DocIdBitSet;
22 
23 namespace Lucene.Net.Search
24 {
25 
26 	/// <summary>Abstract base class for restricting which documents may be returned during searching.</summary>
27 	[Serializable]
28 	public abstract class Filter
29 	{
30 	    ///<summary>
31 	    ///  <para>Creates a <see cref="DocIdSet" /> enumerating the documents that should be
32 	    ///  permitted in search results. <b>NOTE:</b> null can be
33 	    ///  returned if no documents are accepted by this Filter.</para>
34 	    ///  <p/>
35 	    ///  <para>Note: This method will be called once per segment in
36 	    ///  the index during searching.  The returned <see cref="DocIdSet" />
37 	    ///  must refer to document IDs for that segment, not for
38 	    ///  the top-level reader.</para>
39 	    ///</summary>
40 	    /// <returns> a DocIdSet that provides the documents which should be permitted or
41 	    /// prohibited in search results. <b>NOTE:</b> null can be returned if
42 	    /// no documents will be accepted by this Filter.
43 	    /// </returns>
44 	    /// <param name="reader">
45 	    /// A <see cref="IndexReader" /> instance opened on the index currently
46 	    /// searched on. Note, it is likely that the provided reader does not
47 	    /// represent the whole underlying index i.e. if the index has more than
48 	    /// one segment the given reader only represents a single segment.
49 	    /// </param>
50 	    /// <seealso cref="DocIdBitSet">
51 	    /// </seealso>
GetDocIdSet(IndexReader reader)52 	    public abstract DocIdSet GetDocIdSet(IndexReader reader);
53 	}
54 }