1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.directory.server.xdbm.search;
21
22
23 import org.apache.directory.shared.ldap.filter.ExprNode;
24 import org.apache.directory.server.xdbm.IndexEntry;
25
26
27 /**
28 * Evaluates candidate entries to see if they match a filter expression.
29 *
30 * Evaluators contain various overloads to the evaluate method. Often a
31 * developer working in this region of the code may wonder when to use one
32 * override verses another. The overload taking an IndexEntry argument is
33 * specifically suited for use when there is the possibility of multiple entry
34 * lookups from the master table. If the same candidate in the form of an
35 * IndexEntry is evaluated more then this overload is more efficient since it
36 * stores the looked up entry in the IndexEntry preventing multiple lookups.
37 *
38 * If the index entry is already populated with an entry object, and some
39 * evaluation is required then it is preferrable to use the overload that
40 * takes a Long id instead. Likewise if it is known in advance that the
41 * expression is a leaf node built on an indexed attribute then the overload
42 * with the Long id argument is also preferrable unless an IndexEntry already
43 * exists in which case it makes no difference.
44 *
45 * The overload taking the ServerEntry itself is a last resort option and ok
46 * to use when it is known that no index exists for the attributes of
47 * Evaluators based on leaf expressions.
48 *
49 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
50 * @version $Rev: 656489 $
51 */
52 public interface Evaluator<N extends ExprNode,E>
53 {
54 /**
55 * Evaluates a candidate to determine if a filter expression selects it.
56 * If an IndexEntry does has a null reference to the entry object, this
57 * Evaluator may set it if it has to access the full entry within the
58 * master table of the store. Subsequent evaluations on the IndexEntry
59 * then need not access the store to retreive the entry if they need to
60 * access it's attributes.
61 *
62 * @param entry the index record of the entry to evaluate
63 * @return true if filter selects the candidate false otherwise
64 * @throws Exception if there are faults during evaluation
65 */
66 boolean evaluate( IndexEntry<?, E> entry ) throws Exception;
67
68
69 /**
70 * Evaluates whether or not a candidate, specified by an id, satisfies the
71 * expression associated with this Evaluator .
72 *
73 * @param id the identifier for the candidate entry
74 * @return true if filter selects the candidate false otherwise
75 * @throws Exception if there are faults during evaluation
76 */
77 boolean evaluate( Long id ) throws Exception;
78
79
80 /**
81 * Evaluates whether or not a candidate, satisfies the expression
82 * associated with this Evaluator .
83 *
84 * @param entry the candidate entry
85 * @return true if filter selects the candidate false otherwise
86 * @throws Exception if there are faults during evaluation
87 */
88 boolean evaluate( E entry ) throws Exception;
89
90
91 /**
92 * Gets the expression used by this expression Evaluator.
93 *
94 * @return the AST for the expression
95 */
96 N getExpression();
97 }