stream.scotty.core.windowFunction

Interface ReduceAggregateFunction<InputType>

All Superinterfaces:

AggregateFunction<InputType,InputType,InputType>, java.io.Serializable

All Known Subinterfaces:

InvertibleReduceAggregateFunction<Input>

All Known Implementing Classes:

MaxWindowFunction, MinWindowFunction, SumAggregation, SumWindowFunction

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface ReduceAggregateFunction<InputType>
extends AggregateFunction<InputType,InputType,InputType>

Method Summary

Modifier and Type	Method and Description
default InputType	lift(InputType inputTuple) Transforms a tuple to a partial aggregate.
default InputType	lower(InputType aggregate) Transforms a partial aggregate to a final aggregate.

Methods inherited from interface stream.scotty.core.windowFunction.AggregateFunction

combine

Method Detail

lift

default InputType lift(InputType inputTuple)

Description copied from interface: AggregateFunction

Transforms a tuple to a partial aggregate. For example, consider an average computation. If a tuple ⟨p,v⟩ contains its position p and a value v, the lift function will transform it to ⟨sum←v, count←1⟩, which is the partial aggregate of that one tuple.

Specified by:

lift in interface AggregateFunction<InputType,InputType,InputType>

Parameters:

inputTuple - input Tuple

Returns:

PartialAggregate

lower

default InputType lower(InputType aggregate)

Description copied from interface: AggregateFunction

Transforms a partial aggregate to a final aggregate. In our example, the lower function computes the average from sum and count: ⟨sum, count⟩ 7→ sum/count.

Specified by:

lower in interface AggregateFunction<InputType,InputType,InputType>

Returns:

final Aggregate