com.hazelcast.jet.pipeline

Class AggregateBuilder<T0>

java.lang.Object

com.hazelcast.jet.pipeline.AggregateBuilder<T0>

Type Parameters:

T0 - the type of the stream-0 item

public class AggregateBuilder<T0>
extends Object

Offers a step-by-step fluent API to build a pipeline stage that co-aggregates the data from several input stages. To obtain it, call BatchStage.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(BatchStage<E> stage) Adds another stage that will contribute its data to the aggregate operation to be performed.
<A,R> BatchStage<R>	build(AggregateOperation<A,R> aggrOp) Creates and returns a pipeline stage that performs the co-aggregation of 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(BatchStage<E> stage)

Adds another stage that will contribute its data to the aggregate operation to be performed. 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> BatchStage<R> build(AggregateOperation<A,R> aggrOp)

Creates and returns a pipeline stage that performs the co-aggregation of 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,

 BatchStage<A> stage0 = p.drawFrom(Sources.list("a"));
 BatchStage<B> stage1 = p.drawFrom(Sources.list("b"));
 BatchStage<C> stage2 = p.drawFrom(Sources.list("c"));
 BatchStage<D> stage3 = p.drawFrom(Sources.list("d"));

 AggregateBuilder<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);
 BatchStage<Result> resultStage = 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 output item

Parameters:

aggrOp - the aggregate operation to perform

Returns:

a new stage representing the co-aggregation

See Also:

AggregateOperations