Package org.teiid.query.function.aggregate

Source Code of org.teiid.query.function.aggregate.Avg

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* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.  Some portions may be licensed
* to Red Hat, Inc. under one or more contributor license agreements.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA.
*/

package org.teiid.query.function.aggregate;

import java.math.BigDecimal;
import java.util.List;

import org.teiid.api.exception.query.ExpressionEvaluationException;
import org.teiid.api.exception.query.FunctionExecutionException;
import org.teiid.core.TeiidComponentException;
import org.teiid.core.types.DataTypeManager;
import org.teiid.query.QueryPlugin;


/**
* Accumulates (per tuple) and calculates the average of the values
* of a column.  The type of the result varies depending on the type
* of the input {@see AggregateSymbol} - the type will not be an
* integral type but will always be some kind of decimal type.
*/
public class Avg extends Sum {

    private static final int AVG_SCALE = 9;

    private int count = 0;

    /**
     * @see org.teiid.query.function.aggregate.AggregateFunction#initialize(String, Class)
     */
    public void initialize(Class<?> dataType, Class<?> inputType) {
        if (dataType.equals(DataTypeManager.DefaultDataClasses.BIG_DECIMAL)) {
            this.accumulatorType = BIG_DECIMAL;
        } else {
            this.accumulatorType = DOUBLE;
        }
    }

    public void reset() {
        super.reset();
        count = 0;
    }

    /**
     * @see org.teiid.query.function.aggregate.AggregateFunction#addInputDirect(Object, List)
     */
    public void addInputDirect(Object input, List<?> tuple)
        throws FunctionExecutionException, ExpressionEvaluationException, TeiidComponentException {

        super.addInputDirect(input, tuple);
        count++;
    }

    /**
     * @see org.teiid.query.function.aggregate.AggregateFunction#getResult()
     */
    public Object getResult()
        throws FunctionExecutionException, ExpressionEvaluationException, TeiidComponentException {

        Object sum = super.getResult();
        if (count == 0 || sum == null) {
            return null;
        }

        switch(getAccumulatorType()) {
            case DOUBLE:
                return new Double( ((Double)sum).doubleValue() / count );

            case BIG_DECIMAL:
                try {
                    return ((BigDecimal)sum).divide(new BigDecimal(count), AVG_SCALE, BigDecimal.ROUND_HALF_UP);
                } catch(ArithmeticException e) {
                    throw new FunctionExecutionException(e, "ERR.015.001.0048", QueryPlugin.Util.getString("ERR.015.001.0048", sum, new Integer(count))); //$NON-NLS-1$ //$NON-NLS-2$
                }
            default:
                throw new AssertionError("unknown accumulator type"); //$NON-NLS-1$

        }
    }

}
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