01: /*
02: /* $Id: CoalesceFunction.java,v 1.5 2005/12/20 18:32:28 ahimanikya Exp $ tag
03: * =======================================================================
04: * Copyright (c) 2002-2005 Axion Development Team. All rights reserved.
05: *
06: * Redistribution and use in source and binary forms, with or without
07: * modification, are permitted provided that the following conditions
08: * are met:
09: *
10: * 1. Redistributions of source code must retain the above
11: * copyright notice, this list of conditions and the following
12: * disclaimer.
13: *
14: * 2. Redistributions in binary form must reproduce the above copyright
15: * notice, this list of conditions and the following disclaimer in
16: * the documentation and/or other materials provided with the
17: * distribution.
18: *
19: * 3. The names "Tigris", "Axion", nor the names of its contributors may
20: * not be used to endorse or promote products derived from this
21: * software without specific prior written permission.
22: *
23: * 4. Products derived from this software may not be called "Axion", nor
24: * may "Tigris" or "Axion" appear in their names without specific prior
25: * written permission.
26: *
27: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28: * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29: * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
30: * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31: * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
32: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
33: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
37: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38: * =======================================================================
39: */
40:
41: package org.axiondb.functions;
42:
43: import org.axiondb.AxionException;
44: import org.axiondb.DataType;
45: import org.axiondb.FunctionFactory;
46: import org.axiondb.RowDecorator;
47: import org.axiondb.Selectable;
48: import org.axiondb.types.AnyType;
49:
50: /**
51: * <code>COALESCE([<i>value</i>]+)</code>: returns the first non-null value in the
52: * argument list.
53: *
54: * @version $Revision: 1.5 $ $Date: 2005/12/20 18:32:28 $
55: * @author Amrish Lal
56: */
57: public class CoalesceFunction extends BaseFunction implements
58: ScalarFunction, FunctionFactory {
59: public CoalesceFunction() {
60: super ("COALESCE");
61: }
62:
63: public ConcreteFunction makeNewInstance() {
64: return new CoalesceFunction();
65: }
66:
67: public DataType getDataType() {
68: return _returnType != null ? _returnType : ANY_TYPE;
69: }
70:
71: public Object evaluate(RowDecorator row) throws AxionException {
72: Object result = null;
73: Selectable sel = null;
74: for (int i = 0, I = getArgumentCount(); i < I && result == null; i++) {
75: sel = getArgument(i);
76: result = sel.evaluate(row);
77: }
78: _returnType = sel.getDataType();
79: return (result);
80: }
81:
82: public boolean isValid() {
83: return (getArgumentCount() > 0);
84: }
85:
86: private DataType _returnType;
87: private static final DataType ANY_TYPE = AnyType.INSTANCE;
88: }
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