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.api.ldap.model.exception.LdapException; 24 import org.apache.directory.api.ldap.model.filter.ExprNode; 25 import org.apache.directory.server.core.api.partition.PartitionTxn; 26 27 28 /** 29 * An optimizer applies heuristics to determine best execution path to a search 30 * filter based on scan counts within database indices. It annotates the nodes 31 * of an expression subtree by setting a "count" key in the node. Its goal is 32 * to annotate nodes with counts to indicate which nodes to iterate over thereby 33 * minimizing the number cycles in a search. The SearchEngine relies on these 34 * count markers to determine the appropriate path. 35 * 36 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> 37 */ 38 public interface Optimizer 39 { 40 /** 41 * Annotates the expression node tree for optimized traversal metrics. 42 * 43 * @param partitionTxn The transaction to use 44 * @param node the root of the expression node tree 45 * @return The computed value for this node 46 * @throws LdapException if there are failures while optimizing 47 */ 48 Long annotate( PartitionTxn partitionTxn, ExprNode node ) throws LdapException; 49 }