001: /*
002: * $Id: AverageFunction.java,v 1.6 2005/05/02 22:28:41 ahimanikya Exp $
003: * =======================================================================
004: * Copyright (c) 2003-2005 Axion Development Team. All rights reserved.
005: *
006: * Redistribution and use in source and binary forms, with or without
007: * modification, are permitted provided that the following conditions
008: * are met:
009: *
010: * 1. Redistributions of source code must retain the above
011: * copyright notice, this list of conditions and the following
012: * disclaimer.
013: *
014: * 2. Redistributions in binary form must reproduce the above copyright
015: * notice, this list of conditions and the following disclaimer in
016: * the documentation and/or other materials provided with the
017: * distribution.
018: *
019: * 3. The names "Tigris", "Axion", nor the names of its contributors may
020: * not be used to endorse or promote products derived from this
021: * software without specific prior written permission.
022: *
023: * 4. Products derived from this software may not be called "Axion", nor
024: * may "Tigris" or "Axion" appear in their names without specific prior
025: * written permission.
026: *
027: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
028: * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
029: * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
030: * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
031: * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
032: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
033: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
034: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
035: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
036: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
037: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
038: * =======================================================================
039: */
040:
041: package org.axiondb.functions;
042:
043: import java.math.BigDecimal;
044:
045: import org.axiondb.AxionException;
046: import org.axiondb.DataType;
047: import org.axiondb.FunctionFactory;
048: import org.axiondb.RowDecoratorIterator;
049: import org.axiondb.Selectable;
050: import org.axiondb.types.BigDecimalType;
051:
052: /**
053: * @version $Revision: 1.6 $ $Date: 2005/05/02 22:28:41 $
054: * @author Sanjeeth Duvuru
055: * @author Ahimanikya Satapathy
056: */
057: public class AverageFunction extends BaseAggregateFunction implements
058: AggregateFunction, FunctionFactory {
059:
060: public AverageFunction() {
061: super ("AVG");
062: }
063:
064: public ConcreteFunction makeNewInstance() {
065: return new AverageFunction();
066: }
067:
068: public final DataType getDataType() {
069: return _targetType == null ? BIG_DECIMAL_TYPE : _targetType;
070: }
071:
072: public final Object evaluate(RowDecoratorIterator rows)
073: throws AxionException {
074: Selectable sel = getArgument(0);
075: _targetType = sel.getDataType();
076: setDistinct();
077:
078: double rowCount = 0;
079: BigDecimal sum = null;
080: while (rows.hasNext()) {
081: Object val = _targetType.convert(sel.evaluate(rows.next()));
082: if (null != val && acceptable(val)) {
083: rowCount++;
084: sum = evaluate(sum, _targetType.toBigDecimal(val));
085: }
086: }
087:
088: if (null != sum) {
089: return sum.divide(new BigDecimal(rowCount),
090: BigDecimal.ROUND_HALF_UP);
091: }
092: return null;
093: }
094:
095: protected BigDecimal evaluate(BigDecimal src, BigDecimal val) {
096: return null == src ? val : src.add(val);
097: }
098:
099: private DataType _targetType = null;
100: private static final DataType BIG_DECIMAL_TYPE = new BigDecimalType();
101: }
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