cascading.pipe.assembly

Interface AggregateBy.Functor

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

AverageBy.AveragePartials, CountBy.CountPartials, FirstBy.FirstPartials, MaxBy.MaxPartials, MinBy.MinPartials, SumBy.SumPartials

Enclosing class:

AggregateBy

public static interface AggregateBy.Functor
extends java.io.Serializable

Interface Functor provides a means to create a simple function for use with the AggregateBy.CompositeFunction class.

Note the FlowProcess argument provides access to the underlying properties and counter APIs.

Method Summary

Modifier and Type	Method and Description
Tuple	aggregate(FlowProcess flowProcess, TupleEntry args, Tuple context) Method aggregate operates on the given args in tandem (optionally) with the given context values.
Tuple	complete(FlowProcess flowProcess, Tuple context) Method complete allows the final aggregate computation to be performed before the return value is collected.
Fields	getDeclaredFields() Method getDeclaredFields returns the declaredFields of this Functor object.

Method Detail

getDeclaredFields

Fields getDeclaredFields()

Method getDeclaredFields returns the declaredFields of this Functor object.

Returns:

the declaredFields (type Fields) of this Functor object.

aggregate

Tuple aggregate(FlowProcess flowProcess,
                TupleEntry args,
                Tuple context)

Method aggregate operates on the given args in tandem (optionally) with the given context values.

The context argument is the result of the previous call to this method. Use it to store values between aggregate calls (the current count, or sum of the args).

On the very first invocation of aggregate for a given grouping key, context will be null. All subsequent invocations context will be the value returned on the previous invocation.

Parameters:

flowProcess - of type FlowProcess

args - of type TupleEntry

context - of type Tuple @return Tuple

complete

Tuple complete(FlowProcess flowProcess,
               Tuple context)

Method complete allows the final aggregate computation to be performed before the return value is collected.

The number of values in the returned Tuple instance must match the number of declaredFields.

It is safe to return the context object as the result value.

Parameters:

flowProcess - of type FlowProcess

context - of type Tuple @return Tuple