/*
* JBoss, Home of Professional Open Source.
* 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.util.Arrays;
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.query.sql.symbol.AggregateSymbol.Type;
import org.teiid.query.util.CommandContext;
public class StatsFunction extends SingleArgumentAggregateFunction {
private double sum = 0;
private double sumSq = 0;
private long count = 0;
private Type type;
public StatsFunction(Type function) {
this.type = function;
}
@Override
public void reset() {
sum = 0;
sumSq = 0;
count = 0;
}
@Override
public void addInputDirect(Object input, List<?> tuple, CommandContext commandContext)
throws FunctionExecutionException, ExpressionEvaluationException,
TeiidComponentException {
sum += ((Number)input).doubleValue();
sumSq += Math.pow(((Number)input).doubleValue(), 2);
count++;
}
@Override
public Object getResult(CommandContext commandContext) throws FunctionExecutionException,
ExpressionEvaluationException, TeiidComponentException {
double result = 0;
switch (type) {
case STDDEV_POP:
case VAR_POP:
if (count == 0) {
return null;
}
result = (sumSq - sum * sum / count) / count;
if (type == Type.STDDEV_POP) {
result = Math.sqrt(result);
}
break;
case STDDEV_SAMP:
case VAR_SAMP:
if (count < 2) {
return null;
}
result = (sumSq - sum * sum / count) / (count - 1);
if (type == Type.STDDEV_SAMP) {
result = Math.sqrt(result);
}
break;
}
return result;
}
@Override
public void getState(List<Object> state) {
state.add(count);
state.add(sum);
state.add(sumSq);
}
@Override
public List<? extends Class<?>> getStateTypes() {
return Arrays.asList(Long.class, Double.class, Double.class);
}
@Override
public int setState(List<?> state, int index) {
count = (Long) state.get(index++);
sum = (Double) state.get(index++);
sumSq = (Double) state.get(index++);
return index;
}
}