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
25
26 /**
27 * An optimizer applies heuristics to determine best execution path to a search
28 * filter based on scan counts within database indices. It annotates the nodes
29 * of an expression subtree by setting a "count" key in the node. Its goal is
30 * to annotate nodes with counts to indicate which nodes to iterate over thereby
31 * minimizing the number cycles in a search. The SearchEngine relies on these
32 * count markers to determine the appropriate path.
33 *
34 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
35 * @version $Rev: 656041 $
36 */
37 public interface Optimizer
38 {
39 /**
40 * Annotates the expression node tree for optimized traversal metrics.
41 *
42 * @param node the root of the expression node tree
43 * @throws Exception if there are failures while optimizing
44 */
45 Long annotate( ExprNode node ) throws Exception;
46 }