com.hazelcast.jet.pipeline

Class WindowGroupAggregateBuilder<T0,K>

java.lang.Object

com.hazelcast.jet.pipeline.WindowGroupAggregateBuilder<T0,K>

Type Parameters:

T0 - the type of the stream-0 item

K - type of the key

public class WindowGroupAggregateBuilder<T0,K>
extends Object

Offers a step-by-step fluent API to build a pipeline stage that performs a windowed co-grouping and aggregation of the data from several input stages. To obtain it, call StageWithGroupingAndWindow.aggregateBuilder() on one of the stages to co-aggregate, then add the other stages by calling add(stage) on the builder. Collect all the tags returned from add() and use them when building the aggregate operation. Retrieve the tag of the first stage (from which you obtained the builder) by calling tag0().

This object is mainly intended to build a co-aggregation of four or more contributing stages. For up to three stages, prefer the direct stage.aggregateN(...) calls because they offer more static type safety.

Method Summary

Modifier and Type	Method and Description
<E> Tag<E>	add(StreamStageWithGrouping<E,K> stage) Adds another stage that will contribute its data to the windowed group-and-aggregate stage being constructed.
<A,R> StreamStage<TimestampedEntry<K,R>>	build(AggregateOperation<A,R> aggrOp) Convenience for build(AggregateOperation, KeyedWindowResultFunction) which results in a stage that emits TimestampedEntrys.
<A,R,OUT> StreamStage<OUT>	build(AggregateOperation<A,R> aggrOp, KeyedWindowResultFunction<? super K,? super R,OUT> mapToOutputFn) Creates and returns a pipeline stage that performs a windowed cogroup-and-aggregate of the pipeline stages registered with this builder object.
Tag<T0>	tag0() Returns the tag corresponding to the pipeline stage this builder was obtained from.

Methods inherited from class java.lang.Object

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

Method Detail

tag0

public Tag<T0> tag0()

Returns the tag corresponding to the pipeline stage this builder was obtained from. Use this tag to refer to this stage when building the AggregateOperation that you'll pass to build(aggrOp).

add

public <E> Tag<E> add(StreamStageWithGrouping<E,K> stage)

Adds another stage that will contribute its data to the windowed group-and-aggregate stage being constructed. Returns the tag you'll use to refer to this stage when building the AggregateOperation that you'll pass to build().

build

public <A,R,OUT> StreamStage<OUT> build(@Nonnull
                                        AggregateOperation<A,R> aggrOp,
                                        @Nonnull
                                        KeyedWindowResultFunction<? super K,? super R,OUT> mapToOutputFn)

Creates and returns a pipeline stage that performs a windowed cogroup-and-aggregate of the pipeline stages registered with this builder object. The tags you register with the aggregate operation must match the tags you registered with this builder. For example,

 StageWithGroupingAndWindow<A> stage0 =
         streamStage0.window(...).groupingKey(...);
 StreamStageWithGrouping<B> stage1 =
         p.drawFrom(Sources.mapJournal("b", ...)).groupingKey(...);
 StreamStageWithGrouping<C> stage2 =
         p.drawFrom(Sources.mapJournal("c", ...)).groupingKey(...);
 StreamStageWithGrouping<D> stage3 =
         p.drawFrom(Sources.mapJournal("d", ...)).groupingKey(...);

 WindowGroupAggregateBuilder<A> builder = stage0.aggregateBuilder();
 Tag<A> tagA = builder.tag0();
 Tag<B> tagB = builder.add(stage1);
 Tag<C> tagC = builder.add(stage2);
 Tag<D> tagD = builder.add(stage3);
 StreamStage<TimestampedEntry<Result>> = builder.build(AggregateOperation
         .withCreate(MyAccumulator::new)
         .andAccumulate(tagA, MyAccumulator::put)
         .andAccumulate(tagB, MyAccumulator::put)
         .andAccumulate(tagC, MyAccumulator::put)
         .andAccumulate(tagD, MyAccumulator::put)
         .andCombine(MyAccumulator::combine)
         .andFinish(MyAccumulator::finish));
 

Type Parameters:

A - the type of items in the pipeline stage this builder was obtained from

R - the type of the aggregation result

OUT - the type of the output item

Parameters:

aggrOp - the aggregate operation to perform

mapToOutputFn - a function that creates the output item from the aggregation result

Returns:

a new stage representing the co-aggregation

See Also:

AggregateOperations

build

public <A,R> StreamStage<TimestampedEntry<K,R>> build(@Nonnull
                                                      AggregateOperation<A,R> aggrOp)

Convenience for build(AggregateOperation, KeyedWindowResultFunction) which results in a stage that emits TimestampedEntrys. The timestamp of the entry corresponds to the timestamp of the window's end.