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Java > Open Source Codes > org > objectweb > medor > eval > api > NodeEvaluator


1 /**
2  * MEDOR: Middleware Enabling Distributed Object Requests
3  *
4  * Copyright (C) 2001-2004 France Telecom R&D
5  * Contact: alexandre.lefebvre@rd.francetelecom.com
6  *
7  * This library is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * This library is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with this library; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20  *
21  * Initial developers: M. Alia, A. Lefebvre
22  */
23
24 package org.objectweb.medor.eval.api;
25
26 import org.objectweb.medor.api.MedorException;
27 import org.objectweb.medor.expression.api.ParameterOperand;
28 import org.objectweb.medor.query.api.QueryNode;
29 import org.objectweb.medor.tuple.api.TupleCollection;
30 import org.objectweb.medor.eval.prefetch.api.PrefetchBuffer;
31
32 /**
33  * This interface defines the controller object for the evaluation of a given
34  * QueryNode within a QueryTree. It is created at evaluation time by the
35  * NodeEvaluatorFactory, on request from the QueryEvaluator.
36  * The QueryEvaluator controls the overall evaluation by activating/killing
37  * the NodeEvaluator instances.
38  */
39 public interface NodeEvaluator {
40     /**
41      * Closes the links between the current NodeEvaluator and the NodeEvaluators
42      * of the children QueryTrees for pipelining operations.
43      * TODO complete comments
44      */
45     boolean unlinkChildren();
46
47     /**
48      * Opens the links between the current NodeEvaluator and the NodeEvaluators
49      * of the children QueryTrees for pipelining operations.
50      * TODO complete comments
51      */
52     boolean linkChildren();
53
54     /**
55      * This method executes the query on the underlying node.
56      * It controls the evaluation locally for this node.
57      * It returns the TupleCollection containing the result of the execution.
58      */
59     TupleCollection fetchData(ParameterOperand[] parameters)
60         throws MedorException;
61
62     /**
63      * Associates a PrefetchBuffer to be filled by the collection computed by
64      * this evaluator.
65      * @param pb The PrefetchBuffer to be filled.
66      */
67     void setPrefetchBuffer(PrefetchBuffer pb) throws MedorException;
68
69     long getCacheSize();
70
71     void setCacheSize(long cacheSize);
72
73     /**
74      * Returns the evaluation meta data associated with this node evaluator.
75      * @return the associated EvaluationMetaData
76      */
77     EvaluationMetaData getEvaluationMetaData();
78     /**
79      * Returns the QueryNode to which the NodeEvaluator is attached.
80      */
81     QueryNode getQueryNode();
82 }
83
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