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 java.util.ArrayList;
024 import java.util.List;
025
026 import org.apache.directory.server.i18n.I18n;
027 import org.apache.directory.server.xdbm.IndexCursor;
028 import org.apache.directory.server.xdbm.Store;
029 import org.apache.directory.server.xdbm.search.Evaluator;
030 import org.apache.directory.shared.ldap.NotImplementedException;
031 import org.apache.directory.shared.ldap.entry.ServerEntry;
032 import org.apache.directory.shared.ldap.filter.AndNode;
033 import org.apache.directory.shared.ldap.filter.ExprNode;
034 import org.apache.directory.shared.ldap.filter.NotNode;
035 import org.apache.directory.shared.ldap.filter.OrNode;
036 import org.apache.directory.shared.ldap.filter.ScopeNode;
037 import org.apache.directory.shared.ldap.filter.SearchScope;
038
039
040 /**
041 * Builds Cursors over candidates that satisfy a filter expression.
042 *
043 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
044 * @version $Rev: 927146 $
045 */
046 public class CursorBuilder<ID>
047 {
048 /** The database used by this builder */
049 private Store<ServerEntry, ID> db = null;
050
051 /** Evaluator dependency on a EvaluatorBuilder */
052 private EvaluatorBuilder<ID> evaluatorBuilder;
053
054
055 /**
056 * Creates an expression tree enumerator.
057 *
058 * @param db database used by this enumerator
059 * @param evaluatorBuilder the evaluator builder
060 */
061 public CursorBuilder( Store<ServerEntry, ID> db, EvaluatorBuilder<ID> evaluatorBuilder )
062 {
063 this.db = db;
064 this.evaluatorBuilder = evaluatorBuilder;
065 }
066
067
068 public <T> IndexCursor<?, ServerEntry, ID> build( ExprNode node ) throws Exception
069 {
070 switch ( node.getAssertionType() )
071 {
072 /* ---------- LEAF NODE HANDLING ---------- */
073
074 case APPROXIMATE:
075 return new ApproximateCursor<T, ID>( db, ( ApproximateEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
076
077 case EQUALITY:
078 return new EqualityCursor<T, ID>( db, ( EqualityEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
079
080 case GREATEREQ:
081 return new GreaterEqCursor<T, ID>( db, ( GreaterEqEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
082
083 case LESSEQ:
084 return new LessEqCursor<T, ID>( db, ( LessEqEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
085
086 case PRESENCE:
087 return new PresenceCursor<ID>( db, ( PresenceEvaluator<ID> ) evaluatorBuilder.build( node ) );
088
089 case SCOPE:
090 if ( ( ( ScopeNode ) node ).getScope() == SearchScope.ONELEVEL )
091 {
092 return new OneLevelScopeCursor<ID>( db,
093 ( OneLevelScopeEvaluator<ServerEntry, ID> ) evaluatorBuilder.build( node ) );
094 }
095 else
096 {
097 return new SubtreeScopeCursor<ID>( db, ( SubtreeScopeEvaluator<ServerEntry, ID> ) evaluatorBuilder
098 .build( node ) );
099 }
100
101 case SUBSTRING:
102 return new SubstringCursor<ID>( db, ( SubstringEvaluator<ID> ) evaluatorBuilder.build( node ) );
103
104 /* ---------- LOGICAL OPERATORS ---------- */
105
106 case AND:
107 return buildAndCursor( ( AndNode ) node );
108
109 case NOT:
110 return new NotCursor<ID, ID>( db, evaluatorBuilder.build( ( ( NotNode ) node ).getFirstChild() ) );
111
112 case OR:
113 return buildOrCursor( ( OrNode ) node );
114
115 /* ---------- NOT IMPLEMENTED ---------- */
116
117 case ASSERTION:
118 case EXTENSIBLE:
119 throw new NotImplementedException();
120
121 default:
122 throw new IllegalStateException( I18n.err( I18n.ERR_260, node.getAssertionType() ) );
123 }
124 }
125
126
127 /**
128 * Creates a OrCursor over a disjunction expression branch node.
129 *
130 * @param node the disjunction expression branch node
131 * @return Cursor over candidates satisfying disjunction expression
132 * @throws Exception on db access failures
133 */
134 private IndexCursor<?, ServerEntry, ID> buildOrCursor( OrNode node ) throws Exception
135 {
136 List<ExprNode> children = node.getChildren();
137 List<IndexCursor<? extends Object, ServerEntry, ID>> childCursors = new ArrayList<IndexCursor<?, ServerEntry, ID>>(
138 children.size() );
139 List<Evaluator<? extends ExprNode, ServerEntry, ID>> childEvaluators = new ArrayList<Evaluator<? extends ExprNode, ServerEntry, ID>>(
140 children.size() );
141
142 // Recursively create Cursors and Evaluators for each child expression node
143 for ( ExprNode child : children )
144 {
145 childCursors.add( build( child ) );
146 childEvaluators.add( evaluatorBuilder.build( child ) );
147 }
148
149 return new OrCursor( childCursors, childEvaluators );
150 }
151
152
153 /**
154 * Creates an AndCursor over a conjunction expression branch node.
155 *
156 * @param node a conjunction expression branch node
157 * @return Cursor over the conjunction expression
158 * @throws Exception on db access failures
159 */
160 private IndexCursor<?, ServerEntry, ID> buildAndCursor( AndNode node ) throws Exception
161 {
162 int minIndex = 0;
163 long minValue = Long.MAX_VALUE;
164 //noinspection UnusedAssignment
165 long value = Long.MAX_VALUE;
166
167 /*
168 * We scan the child nodes of a branch node searching for the child
169 * expression node with the smallest scan count. This is the child
170 * we will use for iteration by creating a Cursor over its expression.
171 */
172 final List<ExprNode> children = node.getChildren();
173
174 for ( int ii = 0; ii < children.size(); ii++ )
175 {
176 ExprNode child = children.get( ii );
177 Object count = child.get( "count" );
178 if ( count == null )
179 {
180 continue;
181 }
182 value = ( Long ) count;
183 minValue = Math.min( minValue, value );
184
185 if ( minValue == value )
186 {
187 minIndex = ii;
188 }
189 }
190
191 // Once found we build the child Evaluators minus the one for the minChild
192 ExprNode minChild = children.get( minIndex );
193 List<Evaluator<? extends ExprNode, ServerEntry, ID>> childEvaluators = new ArrayList<Evaluator<? extends ExprNode, ServerEntry, ID>>(
194 children.size() - 1 );
195 for ( ExprNode child : children )
196 {
197 if ( child == minChild )
198 {
199 continue;
200 }
201
202 childEvaluators.add( evaluatorBuilder.build( child ) );
203 }
204
205 // Do recursive call to build min child Cursor then create AndCursor
206 IndexCursor<?, ServerEntry, ID> childCursor = build( minChild );
207 return new AndCursor( childCursor, childEvaluators );
208 }
209 }