org.apache.derby.impl.sql.compile
Class SumAvgAggregateDefinition

java.lang.Object
  org.apache.derby.impl.sql.compile.SumAvgAggregateDefinition

All Implemented Interfaces:

AggregateDefinition

public class SumAvgAggregateDefinition
extends java.lang.Object
implements AggregateDefinition

Defintion for the SUM()/AVG() aggregates.

Field Summary

private boolean

isSum

Constructor Summary

SumAvgAggregateDefinition()
Niladic constructor.

Method Summary

DataTypeDescriptor	getAggregator(DataTypeDescriptor inputType, java.lang.StringBuffer aggregatorClass) Determines the result datatype.
private java.lang.String	getAggregatorClassName() Return the aggregator class.
protected java.lang.String	getOperator() Return the arithmetic operator corresponding to this operation.
void	setSumOrAvg(boolean isSum) This is set by the parser.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

isSum

private boolean isSum

Constructor Detail

SumAvgAggregateDefinition

public SumAvgAggregateDefinition()

Niladic constructor. Does nothing. For ease Of use, only.

Method Detail

getAggregator

public final DataTypeDescriptor getAggregator(DataTypeDescriptor inputType,
                                              java.lang.StringBuffer aggregatorClass)

Determines the result datatype. Accept NumberDataValues only.

Note: In the future you should be able to do a sum user data types. One option would be to run sum on anything that implements plus(). In which case avg() would need divide().

Specified by:

getAggregator in interface AggregateDefinition

Parameters:

inputType - the input type, either a user type or a java.lang object

aggregatorClass - output parameter, filled in with the class name that implements com.ibm.db2j.aggregates.Aggregator

Returns:

the output Class (null if cannot operate on value expression of this type.

See Also:

TypeDescriptor

getAggregatorClassName

private java.lang.String getAggregatorClassName()

Return the aggregator class.

Returns:

SumAggregator.CLASS_NAME/AvgAggregator.CLASS_NAME

getOperator

protected java.lang.String getOperator()

Return the arithmetic operator corresponding to this operation.

Returns:

TypeCompiler.SUM_OP /TypeCompiler.AVG_OP

setSumOrAvg

public final void setSumOrAvg(boolean isSum)

This is set by the parser.