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Java > Open Source Codes > com > caucho > db > sql > StringEqExpr


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.db.sql;
30
31 import com.caucho.log.Log;
32
33 import java.sql.SQLException JavaDoc;
34 import java.util.ArrayList JavaDoc;
35 import java.util.logging.Logger JavaDoc;
36
37 class StringEqExpr extends Expr {
38   private static final Logger JavaDoc log = Log.open(StringEqExpr.class);
39
40   private ColumnExpr _column;
41   private Expr _right;
42
43   StringEqExpr(ColumnExpr left, Expr right)
44   {
45     _column = left;
46     _right = right;
47   }
48
49   protected Expr bind(Query query)
50     throws SQLException JavaDoc
51   {
52     throw new UnsupportedOperationException JavaDoc();
53   }
54
55   /**
56    * Returns the cost based on the given FromList.
57    */
58   public long subCost(ArrayList JavaDoc<FromItem> fromList)
59   {
60     return _column.subCost(fromList) + _right.subCost(fromList);
61   }
62
63   /**
64    * Returns the type of the expression.
65    */
66   public Class JavaDoc getType()
67   {
68     return boolean.class;
69   }
70
71   /**
72    * Returns true for a null value.
73    */
74   public boolean isNull(QueryContext context)
75     throws SQLException JavaDoc
76   {
77     return _column.isNull(context);
78   }
79
80   /**
81    * Evaluates the expression as a boolean.
82    */
83   public int evalBoolean(QueryContext context)
84     throws SQLException JavaDoc
85   {
86     if (_right.isNull(context))
87       return UNKNOWN;
88     else if (_column.isNull(context))
89       return UNKNOWN;
90     
91     if (_column.evalEqual(context, _right.evalString(context)))
92       return TRUE;
93     else
94       return FALSE;
95   }
96
97   public String JavaDoc evalString(QueryContext context)
98     throws SQLException JavaDoc
99   {
100     throw new SQLException JavaDoc("can't convert string to boolean");
101   }
102
103   public String JavaDoc toString()
104   {
105     return "(" + _column + " = " + _right + ")";
106   }
107 }
108
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