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.OrNode;
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 disjunction (OR) expressions.
037 *
038 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
039 * @version $$Rev$$
040 */
041 public class OrEvaluator<ID> implements Evaluator<OrNode, ServerEntry, ID>
042 {
043 private final List<Evaluator<? extends ExprNode, ServerEntry, ID>> evaluators;
044
045 private final OrNode node;
046
047
048 public OrEvaluator( OrNode 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 * decreasing scan counts on their expression nodes. This is done to have
058 * the Evaluators with the greatest scan counts which have the highest
059 * probability of accepting 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 decreasing 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<? extends ExprNode, ServerEntry, ID>>()
073 {
074 public int compare( Evaluator<? extends ExprNode, ServerEntry, ID> e1,
075 Evaluator<? extends ExprNode, ServerEntry, ID> e2 )
076 {
077 long scanCount1 = ( Long ) e1.getExpression().get( "count" );
078 long scanCount2 = ( Long ) e2.getExpression().get( "count" );
079
080 if ( scanCount1 == scanCount2 )
081 {
082 return 0;
083 }
084
085 /*
086 * We want the Evaluator with the largest scan count first
087 * since this node has the highest probability of accepting,
088 * or rather the least probability of failing. That way we
089 * can short the sub-expression evaluation process.
090 */
091 if ( scanCount1 < scanCount2 )
092 {
093 return 1;
094 }
095
096 return -1;
097 }
098 } );
099
100 return optimized;
101 }
102
103
104 public boolean evaluate( IndexEntry<?, ServerEntry, ID> indexEntry ) throws Exception
105 {
106 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
107 {
108 if ( evaluator.evaluate( indexEntry ) )
109 {
110 return true;
111 }
112 }
113
114 return false;
115 }
116
117
118 public boolean evaluateId( ID id ) throws Exception
119 {
120 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
121 {
122 if ( evaluator.evaluateId( id ) )
123 {
124 return true;
125 }
126 }
127
128 return false;
129 }
130
131
132 public boolean evaluateEntry( ServerEntry entry ) throws Exception
133 {
134 for ( Evaluator<?, ServerEntry, ID> evaluator : evaluators )
135 {
136 if ( evaluator.evaluateEntry( entry ) )
137 {
138 return true;
139 }
140 }
141
142 return false;
143 }
144
145
146 public OrNode getExpression()
147 {
148 return node;
149 }
150 }