Package org.apache.flink.api.common.functions

Class RichAggregateFunction<IN,ACC,OUT>

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichAggregateFunction<IN,ACC,OUT>

Type Parameters:

IN - The type of the values that are aggregated (input values)

ACC - The type of the accumulator (intermediate aggregate state).

OUT - The type of the aggregated result

All Implemented Interfaces:

Serializable, AggregateFunction<IN,ACC,OUT>, Function, RichFunction

@PublicEvolving
public abstract class RichAggregateFunction<IN,ACC,OUT>
extends AbstractRichFunction
implements AggregateFunction<IN,ACC,OUT>

Rich variant of the AggregateFunction. As a RichFunction, it gives access to the RuntimeContext and provides setup and teardown methods: RichFunction.open(OpenContext) and RichFunction.close().

See Also:

AggregateFunction, Serialized Form

Constructor Summary

Constructors

Constructor	Description
RichAggregateFunction()

Method Summary

Modifier and Type	Method	Description
abstract ACC	add(IN value, ACC accumulator)	Adds the given input value to the given accumulator, returning the new accumulator value.
abstract ACC	createAccumulator()	Creates a new accumulator, starting a new aggregate.
abstract OUT	getResult(ACC accumulator)	Gets the result of the aggregation from the accumulator.
abstract ACC	merge(ACC a, ACC b)	Merges two accumulators, returning an accumulator with the merged state.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RichAggregateFunction

public RichAggregateFunction()

Method Detail

createAccumulator

public abstract ACC createAccumulator()

Description copied from interface: AggregateFunction

Creates a new accumulator, starting a new aggregate.

The new accumulator is typically meaningless unless a value is added via AggregateFunction.add(Object, Object).

The accumulator is the state of a running aggregation. When a program has multiple aggregates in progress (such as per key and window), the state (per key and window) is the size of the accumulator.

Specified by:

createAccumulator in interface AggregateFunction<IN,ACC,OUT>

Returns:

A new accumulator, corresponding to an empty aggregate.

add

public abstract ACC add(IN value,
                        ACC accumulator)

Description copied from interface: AggregateFunction

Adds the given input value to the given accumulator, returning the new accumulator value.

For efficiency, the input accumulator may be modified and returned.

Specified by:

add in interface AggregateFunction<IN,ACC,OUT>

Parameters:

value - The value to add

accumulator - The accumulator to add the value to

Returns:

The accumulator with the updated state

getResult

public abstract OUT getResult(ACC accumulator)

Description copied from interface: AggregateFunction

Gets the result of the aggregation from the accumulator.

Specified by:

getResult in interface AggregateFunction<IN,ACC,OUT>

Parameters:

accumulator - The accumulator of the aggregation

Returns:

The final aggregation result.

merge

public abstract ACC merge(ACC a,
                          ACC b)

Description copied from interface: AggregateFunction

Merges two accumulators, returning an accumulator with the merged state.

This function may reuse any of the given accumulators as the target for the merge and return that. The assumption is that the given accumulators will not be used any more after having been passed to this function.

Specified by:

merge in interface AggregateFunction<IN,ACC,OUT>

Parameters:

a - An accumulator to merge

b - Another accumulator to merge

Returns:

The accumulator with the merged state