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Java > Open Source Codes > com > db4o > config > QueryEvaluationMode


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.config;
22
23
24 /**
25  * This class provides static constants for the query evaluation
26  * modes that db4o supports.
27  * <br><br><b>For detailed documentation please see
28  * {@link QueryConfiguration#evaluationMode(QueryEvaluationMode)}</b>
29  */
30 public class QueryEvaluationMode {
31     
32     private QueryEvaluationMode(){
33         
34     }
35     
36     /**
37      * Constant for immediate query evaluation. The query is executed fully
38      * when Query#execute() is called.
39      * <br><br><b>For detailed documentation please see
40      * {@link QueryConfiguration#evaluationMode(QueryEvaluationMode)}</b>
41      */
42     public static final QueryEvaluationMode IMMEDIATE = new QueryEvaluationMode();
43
44     /**
45      * Constant for snapshot query evaluation. When Query#execute() is called,
46      * the query processor chooses the best indexes, does all index processing
47      * and creates a snapshot of the index at this point in time. Non-indexed
48      * constraints are evaluated lazily when the application iterates through
49      * the {@link ObjectSet} resultset of the query.
50      * <br><br><b>For detailed documentation please see
51      * {@link QueryConfiguration#evaluationMode(QueryEvaluationMode)}</b>
52      */
53     public static final QueryEvaluationMode SNAPSHOT = new QueryEvaluationMode();
54     
55     /**
56      * Constant for lazy query evaluation. When Query#execute() is called, the
57      * query processor only chooses the best index and creates an iterator on
58      * this index. Indexes and constraints are evaluated lazily when the
59      * application iterates through the {@link ObjectSet} resultset of the query.
60      * <br><br><b>For detailed documentation please see
61      * {@link QueryConfiguration#evaluationMode(QueryEvaluationMode)}</b>
62      */
63     public static final QueryEvaluationMode LAZY = new QueryEvaluationMode();
64     
65     
66     private static final QueryEvaluationMode[] MODES = new QueryEvaluationMode[] {
67         QueryEvaluationMode.IMMEDIATE,
68         QueryEvaluationMode.SNAPSHOT,
69         QueryEvaluationMode.LAZY,
70     };
71     
72     /**
73      * internal method, ignore please.
74      */
75     public int asInt(){
76         for (int i = 0; i < MODES.length; i++) {
77             if(MODES[i] == this){
78                 return i;
79             }
80         }
81         throw new IllegalStateException JavaDoc();
82     }
83     
84     /**
85      * internal method, ignore please.
86      */
87     public static QueryEvaluationMode fromInt(int i){
88         return MODES[i];
89     }
90
91 }
92
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