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package com.salesforce.phoenix.expression.function;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import com.salesforce.phoenix.expression.Expression;
import com.salesforce.phoenix.expression.aggregator.Aggregator;
import com.salesforce.phoenix.expression.aggregator.DecimalStddevSampAggregator;
import com.salesforce.phoenix.expression.aggregator.DistinctValueWithCountClientAggregator;
import com.salesforce.phoenix.expression.aggregator.DistinctValueWithCountServerAggregator;
import com.salesforce.phoenix.expression.aggregator.StddevSampAggregator;
import com.salesforce.phoenix.parse.FunctionParseNode.Argument;
import com.salesforce.phoenix.parse.FunctionParseNode.BuiltInFunction;
import com.salesforce.phoenix.schema.PDataType;
/**
*
* Built-in function for STDDEV_SAMP(<expression>) aggregate function
*
* @author anoopsjohn
* @since 1.2.1
*/
@BuiltInFunction(name = StddevSampFunction.NAME, args = { @Argument(allowedTypes={PDataType.DECIMAL})})
public class StddevSampFunction extends DistinctValueWithCountAggregateFunction {
public static final String NAME = "STDDEV_SAMP";
public StddevSampFunction() {
}
public StddevSampFunction(List<Expression> childern) {
super(childern);
}
@Override
public Aggregator newServerAggregator(Configuration conf) {
return new DistinctValueWithCountServerAggregator(conf);
}
@Override
public DistinctValueWithCountClientAggregator newClientAggregator() {
if (children.get(0).getDataType() == PDataType.DECIMAL) {
// Special Aggregators for DECIMAL datatype for more precision than double
return new DecimalStddevSampAggregator(children, getAggregatorExpression().getColumnModifier());
}
return new StddevSampAggregator(children, getAggregatorExpression().getColumnModifier());
}
@Override
public String getName() {
return NAME;
}
@Override
public PDataType getDataType() {
return PDataType.DECIMAL;
}
}