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


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 ConcatExpr extends Expr {
38   private static final Logger JavaDoc log = Log.open(ConcatExpr.class);
39
40   private Expr _left;
41   private Expr _right;
42
43   ConcatExpr(Expr left, Expr right)
44   {
45     _left = left;
46     _right = right;
47   }
48
49   protected Expr bind(Query query)
50     throws SQLException JavaDoc
51   {
52     _left = _left.bind(query);
53     _right = _right.bind(query);
54
55     return this;
56   }
57
58   /**
59    * Returns the type of the expression.
60    */
61   public Class JavaDoc getType()
62   {
63     return String JavaDoc.class;
64   }
65
66   /**
67    * Returns the cost based on the given FromList.
68    */
69   public long subCost(ArrayList JavaDoc<FromItem> fromList)
70   {
71     return _left.subCost(fromList) + _right.subCost(fromList);
72   }
73
74   /**
75    * Evaluates the expression as a string.
76    */
77   public String JavaDoc evalString(QueryContext context)
78     throws SQLException JavaDoc
79   {
80     String JavaDoc leftValue = _left.evalString(context);
81     String JavaDoc rightValue = _right.evalString(context);
82
83     if (leftValue == null)
84       return rightValue;
85
86     if (rightValue == null)
87       return leftValue;
88
89     return leftValue + rightValue;
90   }
91
92   /**
93    * Evaluates aggregate functions during the group phase.
94    *
95    * @param state the current database tuple
96    */
97   public void evalGroup(QueryContext context)
98     throws SQLException JavaDoc
99   {
100     _left.evalGroup(context);
101     _right.evalGroup(context);
102   }
103
104   public String JavaDoc toString()
105   {
106     return "(" + _left + " || " + _right + ")";
107   }
108 }
109
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