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

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

All Implemented Interfaces:

AggregateDefinition

public class MaxMinAggregateDefinition
extends java.lang.Object
implements AggregateDefinition

Defintion for the MAX()/MIN() aggregates.

Field Summary

private boolean

isMax

Constructor Summary

MaxMinAggregateDefinition()
Niladic constructor.

Method Summary

DataTypeDescriptor	getAggregator(DataTypeDescriptor inputType, java.lang.StringBuffer aggregatorClass) Determines the result datatype.
boolean	isMax() Return if the aggregator class is for min/max.
void	setMaxOrMin(boolean isMax) 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

isMax

private boolean isMax

Constructor Detail

MaxMinAggregateDefinition

public MaxMinAggregateDefinition()

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 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

setMaxOrMin

public final void setMaxOrMin(boolean isMax)

This is set by the parser.

isMax

public final boolean isMax()

Return if the aggregator class is for min/max.

Returns:

boolean true/false