cascading.pipe.assembly
Interface AggregateBy.Functor

All Superinterfaces:
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 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
 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


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