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Java > Open Source Codes > org > apache > ldap > server > db > Optimizer


1 /*
2  * Copyright 2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package org.apache.ldap.server.db;
18
19
20 import org.apache.ldap.common.filter.ExprNode;
21
22 import javax.naming.NamingException JavaDoc;
23
24
25 /**
26  * An optimizer applies heuristics to determine best execution path to a search
27  * filter based on scan counts within database indices. It annotates the nodes
28  * of an expression subtree by setting a "count" key in the node. Its goal is
29  * to annotate nodes with counts to indicate which nodes to iterate over thereby
30  * minimizing the number cycles in a search. The SearchEngine relies on these
31  * count markers to determine the appropriate path.
32  *
33  * @author <a HREF="mailto:dev@directory.apache.org">Apache Directory Project</a>
34  * @version $Rev: 169198 $
35  */
36 public interface Optimizer
37 {
38     /**
39      * Annotates the expression node tree for optimized traversal metrics.
40      *
41      * @param node the root of the expression node tree
42      * @throws NamingException if there are failures while optimizing
43      */
44     void annotate( ExprNode node ) throws NamingException JavaDoc;
45 }
46
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