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


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 import com.caucho.util.L10N;
33
34 import java.sql.SQLException JavaDoc;
35 import java.util.ArrayList JavaDoc;
36 import java.util.logging.Logger JavaDoc;
37
38 public class ExistsEvalExpr extends Expr {
39   protected static final L10N L = new L10N(ExistsEvalExpr.class);
40   private static final Logger JavaDoc log = Log.open(ExistsEvalExpr.class);
41
42   private ExistsExpr _subselect;
43   
44   ExistsEvalExpr(ExistsExpr subselect)
45   {
46     _subselect = subselect;
47   }
48
49   /**
50    * Returns the expected result type of the expression.
51    */
52   public Class JavaDoc getType()
53   {
54     return boolean.class;
55   }
56
57   /**
58    * Returns the cost based on the given FromList.
59    */
60   public long subCost(ArrayList JavaDoc<FromItem> fromList)
61   {
62     return _subselect.subCost(fromList) - 1;
63   }
64
65   /**
66    * Evaluates the expression as a boolean.
67    *
68    * @param rows the current database tuple
69    *
70    * @return the string value
71    */
72   public int evalBoolean(QueryContext context)
73     throws SQLException JavaDoc
74   {
75     _subselect.evaluate(context);
76
77     return TRUE;
78   }
79
80   /**
81    * Evaluates the expression as a string.
82    *
83    * @param rows the current database tuple
84    *
85    * @return the string value
86    */
87   public String JavaDoc evalString(QueryContext context)
88     throws SQLException JavaDoc
89   {
90     throw new UnsupportedOperationException JavaDoc();
91   }
92
93   public String JavaDoc toString()
94   {
95     return "ExistsEvalExpr[" + _subselect + "]";
96   }
97 }
98
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