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


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.io.IOException JavaDoc;
42
43 import java.util.Enumeration JavaDoc;
44
45 import java.sql.SQLException JavaDoc;
46
47 import com.quadcap.util.Debug;
48
49 /**
50  * Implementation of the SQL <B>DROP CONSTRAINT</B> statement.
51  *
52  * @author Stan Bailes
53  */
54 public class StmtDropConstraint implements Stmt {
55     String JavaDoc tableName;
56     String JavaDoc constraintName;
57     boolean restrict;
58
59     public StmtDropConstraint(String JavaDoc tableName, String JavaDoc constraintName,
60                   boolean restrict) {
61     this.tableName = tableName;
62     this.constraintName = constraintName;
63     this.restrict = restrict;
64     }
65
66     public void execute(Session session) throws IOException JavaDoc, SQLException JavaDoc {
67     session.getTableWriteLock("#Schema");
68     session.getTableWriteLock(tableName);
69     Database db = session.getDatabase();
70     Table table = (Table)db.getRelation(tableName);
71     if (table == null) {
72         throw new SQLException JavaDoc("table not found: " + tableName);
73     }
74     Constraint constraint = table.getConstraint(constraintName);
75     if (constraint == null) {
76         throw new SQLException JavaDoc("constraint not found: " + constraintName);
77     }
78     if (restrict) {
79         if (constraint instanceof UniqueConstraint) {
80         UniqueConstraint uc = (UniqueConstraint)constraint;
81         Enumeration JavaDoc en = uc.getExportConstraints();
82         if (en.hasMoreElements()) {
83             throw new SQLException JavaDoc("Can't drop unique/primary key " +
84                        "because of referencing foreign " +
85                        "key constraints");
86         }
87         }
88     } else {
89         if (constraint instanceof UniqueConstraint) {
90         UniqueConstraint uc = (UniqueConstraint)constraint;
91         Enumeration JavaDoc en = uc.getExportConstraints();
92         while (en.hasMoreElements()) {
93             String JavaDoc name = (String JavaDoc)en.nextElement().toString();
94             ExportedKeyConstraint ec =
95             (ExportedKeyConstraint)table.getConstraint(name);
96             session.doStep(new DeleteConstraint(session, table, ec));
97             DeleteConstraint.deleteForeign(session, ec);
98         }
99         }
100     }
101
102     // --- if we're about to delete the last unique/primary key constraint,
103 // --- we have to create a DefaultTableConstraint so there's some
104 // --- kind of index.
105 if (constraint instanceof IndexConstraint) {
106         int icnt = 0;
107             int num = table.getNumConstraints();
108             for (int i = 0; i < num; i++) {
109                 Constraint c = table.getConstraint(i);
110                 if (c instanceof IndexConstraint) icnt++;
111             }
112         if (icnt == 1) {
113         DefaultTableConstraint con = new DefaultTableConstraint();
114         con.setTable(table);
115         table.nameConstraint(con);
116         session.doStep(new AddConstraint(session, table, con));
117         }
118     }
119     session.doStep(new DeleteConstraint(session, table, constraint));
120     DeleteConstraint.deleteForeign(session, constraint);
121
122     }
123
124 }
125
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