01: /*
02: * $Id: ComparableAggregateFunction.java,v 1.1 2005/08/24 00:41:52 ahimanikya Exp $
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.RowDecoratorIterator;
46: import org.axiondb.Selectable;
47: import org.axiondb.types.AnyType;
48:
49: /**
50: * @version $Revision: 1.1 $ $Date: 2005/08/24 00:41:52 $
51: * @author Rodney Waldhoff
52: * @author Ahimanikya Satapathy
53: */
54: public abstract class ComparableAggregateFunction extends
55: BaseAggregateFunction implements AggregateFunction {
56: public ComparableAggregateFunction(String name) {
57: super (name);
58: }
59:
60: public final DataType getDataType() {
61: return _targetType == null ? ANY_TYPE : _targetType;
62: }
63:
64: public final Object evaluate(RowDecoratorIterator rows)
65: throws AxionException {
66: Comparable result = null;
67: Selectable sel = getArgument(0);
68: _targetType = sel.getDataType();
69: setDistinct();
70:
71: while (rows.hasNext()) {
72: Object rawVal = sel.evaluate(rows.next());
73: DataType currentType = sel.getDataType();
74: Object val = currentType.convert(rawVal);
75: if (null != val && acceptable(val)) {
76: result = evaluate(result, (Comparable) val);
77: }
78: }
79: return null != result ? result : null;
80: }
81:
82: protected abstract Comparable evaluate(Comparable src,
83: Comparable val);
84:
85: private DataType _targetType = null;
86: private static final DataType ANY_TYPE = new AnyType();
87: }
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