com.celequest.api.function
Interface IUDAggregateState

All Superinterfaces:

Serializable

public interface IUDAggregateState

extends Serializable

This interface encapsulates the state required to compute the aggregate value for an aggregate function. The implementation depends on the requirements of the aggregate function. For example, the aggregate state for the AVG function need only keep track of a sum and count of all consumed values. Each time a new value is inserted, it is added to the sum and the count is incremented. Each time a value is deleted, it is subtracted from the sum and the count is decremented.

Note that implementors of this interface must also implement the java.io.Serializable interface. This is required so that the aggregate state can be persisted. You may elect to implement the java.io.Externalizable interface instead. Failure to provide meaningful implementations of either of these interfaces may result in incorrect behavior for check-point and recovery among other features.

Since:

2.5.3

Version:

$Revision: #3 $, $Date: 2007/04/26 $

Method Summary

int	getCount() Return consumed value count.

Method Detail

getCount

public int getCount()

Return consumed value count. This should be equal to the number of inserted values less the number of deleted values (including null values).

Returns:

a non-negative integer