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Java > Open Source Codes > com > quadcap > sql > StmtUpdate


1 package com.quadcap.sql;
2
3 /* Copyright 1999 - 2003 Quadcap Software. All rights reserved.
4  *
5  * This software is distributed under the Quadcap Free Software License.
6  * This software may be used or modified for any purpose, personal or
7  * commercial. Open Source redistributions are permitted. Commercial
8  * redistribution of larger works derived from, or works which bundle
9  * this software requires a "Commercial Redistribution License"; see
10  * http://www.quadcap.com/purchase.
11  *
12  * Redistributions qualify as "Open Source" under one of the following terms:
13  *
14  * Redistributions are made at no charge beyond the reasonable cost of
15  * materials and delivery.
16  *
17  * Redistributions are accompanied by a copy of the Source Code or by an
18  * irrevocable offer to provide a copy of the Source Code for up to three
19  * years at the cost of materials and delivery. Such redistributions
20  * must allow further use, modification, and redistribution of the Source
21  * Code under substantially the same terms as this license.
22  *
23  * Redistributions of source code must retain the copyright notices as they
24  * appear in each source code file, these license terms, and the
25  * disclaimer/limitation of liability set forth as paragraph 6 below.
26  *
27  * Redistributions in binary form must reproduce this Copyright Notice,
28  * these license terms, and the disclaimer/limitation of liability set
29  * forth as paragraph 6 below, in the documentation and/or other materials
30  * provided with the distribution.
31  *
32  * The Software is provided on an "AS IS" basis. No warranty is
33  * provided that the Software is free of defects, or fit for a
34  * particular purpose.
35  *
36  * Limitation of Liability. Quadcap Software shall not be liable
37  * for any damages suffered by the Licensee or any third party resulting
38  * from use of the Software.
39  */
40
41 import java.util.Vector JavaDoc;
42
43 import java.io.IOException JavaDoc;
44
45 import java.sql.ResultSet JavaDoc;
46 import java.sql.SQLException JavaDoc;
47
48 import com.quadcap.util.Debug;
49
50 /**
51  * Implementation of the SQL <b>UPDATE</b> statement.
52  *
53  * @author Stan Bailes
54  */
55
56 public class StmtUpdate implements Stmt {
57     String JavaDoc tableName;
58     SelectExpression select;
59     Vector JavaDoc items;
60
61     /**
62      * Default constructor
63      */
64     public StmtUpdate() {}
65
66     /**
67      * Explicit constructor from table name only
68      */
69     public StmtUpdate(String JavaDoc tableName) {
70     this.tableName = tableName;
71     this.items = new Vector JavaDoc();
72     }
73
74     /**
75      * Add a new update item
76      */
77     public void addItem(UpdateItem item) {
78     items.addElement(item);
79     }
80
81     /**
82      * Add a 'where' expression
83      */
84     public void addWhere(Expression where) {
85     select = new SelectExpression(tableName, where);
86     }
87
88     /**
89      * Excute the update operation
90      */
91     public void execute(Session session) throws IOException JavaDoc, SQLException JavaDoc {
92         Database db = session.getDatabase();
93         Relation t = db.getRelation(tableName);
94         if (t == null) {
95             throw new SQLException JavaDoc("No such table/view: " + tableName,
96                                    "42000");
97         }
98         if (!t.isUpdatable()) {
99             throw new SQLException JavaDoc("Not updatable: " + tableName,
100                                    "42000");
101         }
102         session.getTableWriteLock(tableName);
103         Cursor updateCursor = TableOps.getCursor(session, t, select);
104         try {
105             while (updateCursor.next()) {
106                 Row row = updateCursor.getRow();
107                 for (int i = 0; i < items.size(); i++) {
108                     UpdateItem item = (UpdateItem)items.elementAt(i);
109                     item.evaluate(session, t, updateCursor);
110                 }
111                 for (int i = 0; i < items.size(); i++) {
112                     UpdateItem item = (UpdateItem)items.elementAt(i);
113                     item.update(session, row);
114                 }
115                 session.clearViewCheck();
116                 updateCursor.updateRow(row); // ZZZ hot
117 }
118         } finally {
119             updateCursor.close();
120         }
121     }
122 }
123
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