001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied. See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 *
019 */
020 package org.apache.directory.server.xdbm.search.impl;
021
022
023 import org.apache.directory.shared.ldap.entry.ServerEntry;
024 import org.apache.directory.shared.ldap.filter.AndNode;
025 import org.apache.directory.shared.ldap.filter.ExprNode;
026 import org.apache.directory.server.xdbm.IndexEntry;
027 import org.apache.directory.server.xdbm.search.Evaluator;
028
029 import java.util.List;
030 import java.util.ArrayList;
031 import java.util.Collections;
032 import java.util.Comparator;
033
034
035 /**
036 * An Evaluator for logical conjunction (AND) expressions.
037 *
038 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
039 * @version $$Rev$$
040 */
041 public class AndEvaluator<ID> implements Evaluator<AndNode, ServerEntry, ID>
042 {
043 private final List<Evaluator<? extends ExprNode, ServerEntry, ID>> evaluators;
044
045 private final AndNode node;
046
047
048 public AndEvaluator( AndNode node, List<Evaluator<? extends ExprNode, ServerEntry, ID>> evaluators )
049 {
050 this.node = node;
051 this.evaluators = optimize( evaluators );
052 }
053
054
055 /**
056 * Takes a set of Evaluators and copies then sorts them in a new list with
057 * increasing scan counts on their expression nodes. This is done to have
058 * the Evaluators with the least scan count which have the highest
059 * probability of rejecting a candidate first. That will increase the
060 * chance of shorting the checks on evaluators early so extra lookups and
061 * comparisons are avoided.
062 *
063 * @param unoptimized the unoptimized list of Evaluators
064 * @return optimized Evaluator list with increasing scan count ordering
065 */
066 private List<Evaluator<? extends ExprNode, ServerEntry, ID>> optimize(
067 List<Evaluator<? extends ExprNode, ServerEntry, ID>> unoptimized )
068 {
069 List<Evaluator<? extends ExprNode, ServerEntry, ID>> optimized = new ArrayList<Evaluator<? extends ExprNode, ServerEntry, ID>>(
070 unoptimized.size() );
071 optimized.addAll( unoptimized );
072 Collections.sort( optimized, new Comparator<Evaluator<?, ServerEntry, ID>>()
073 {
074 public int compare( Evaluator<?, ServerEntry, ID> e1, Evaluator<?, ServerEntry, ID> e2 )
075 {
076 long scanCount1 = ( Long ) e1.getExpression().get( "count" );
077 long scanCount2 = ( Long ) e2.getExpression().get( "count" );
078
079 if ( scanCount1 == scanCount2 )
080 {
081 return 0;
082 }
083
084 /*
085 * We want the Evaluator with the smallest scan count first
086 * since this node has the highest probability of failing, or
087 * rather the least probability of succeeding. That way we
088 * can short the sub-expression evaluation process.
089 */
090 if ( scanCount1 < scanCount2 )
091 {
092 return -1;
093 }
094
095 return 1;
096 }
097 } );
098
099 return optimized;
100 }
101
102
103 public boolean evaluateId( ID id ) throws Exception
104 {
105 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
106 {
107 if ( !evaluator.evaluateId( id ) )
108 {
109 return false;
110 }
111 }
112
113 return true;
114 }
115
116
117 public boolean evaluateEntry( ServerEntry entry ) throws Exception
118 {
119 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
120 {
121 if ( !evaluator.evaluateEntry( entry ) )
122 {
123 return false;
124 }
125 }
126
127 return true;
128 }
129
130
131 public boolean evaluate( IndexEntry<?, ServerEntry, ID> indexEntry ) throws Exception
132 {
133 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
134 {
135 if ( !evaluator.evaluate( indexEntry ) )
136 {
137 return false;
138 }
139 }
140
141 return true;
142 }
143
144
145 public AndNode getExpression()
146 {
147 return node;
148 }
149 }