Top Description Constructors Methods
org.apache.derby.impl.sql.compile

pack-priv Class CountAggregateDefinition

extends Object
implements AggregateDefinition
Class Inheritance
All Implemented Interfaces
org.apache.derby.impl.sql.compile.AggregateDefinition
Imports
org.apache.derby.shared.common.reference.ClassName, org.apache.derby.iapi.types.DataTypeDescriptor
Definition for the COUNT()/COUNT(*) aggregates.

Constructor Summary

AccessConstructor and Description
public
CountAggregateDefinition()

Niladic constructor.

Method Summary

Modifier and TypeMethod and Description
public final DataTypeDescriptor

Returns:

the output Class (null if cannot operate on value expression of this type.
getAggregator(DataTypeDescriptor
the input type, either a user type or a java.lang object
inputType, StringBuffer
output parameter, filled in with the class name that implements com.ibm.db2j.aggregates.Aggregator
aggregatorClass)

Implements org.apache.derby.impl.sql.compile.AggregateDefinition.getAggregator.

Determines the result datatype.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Constructor Detail

CountAggregateDefinitionback to summary
public CountAggregateDefinition()

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

Method Detail

getAggregatorback to summary
public final DataTypeDescriptor getAggregator(DataTypeDescriptor inputType, StringBuffer aggregatorClass)

Implements org.apache.derby.impl.sql.compile.AggregateDefinition.getAggregator.

Determines the result datatype. We can run count() on anything, and it always returns a INTEGER (java.lang.Integer).

Parameters
inputType:DataTypeDescriptor

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

aggregatorClass:StringBuffer

Doc from org.apache.derby.impl.sql.compile.AggregateDefinition.getAggregator.

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

Returns:DataTypeDescriptor

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