com.hazelcast.jet.pipeline.GroupAggregateBuilder Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2018, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.jet.pipeline;
import com.hazelcast.jet.Util;
import com.hazelcast.jet.aggregate.AggregateOperation;
import com.hazelcast.jet.datamodel.Tag;
import com.hazelcast.jet.function.DistributedBiFunction;
import com.hazelcast.jet.impl.pipeline.GrAggBuilder;
import javax.annotation.Nonnull;
import java.util.Map.Entry;
/**
* Offers a step-by-step fluent API to build a pipeline stage that
* co-groups and aggregates the data from several input stages. To obtain
* it, call {@link StageWithGrouping#aggregateBuilder()} on one of the
* stages to co-group, then add the other stages by calling {@link #add
* add(stage)} on the builder. Collect all the tags returned from {@code
* add()} and use them when building the aggregate operation. Retrieve the
* tag of the first stage (from which you obtained the builder) by calling
* {@link #tag0()}.
*
* This object is mainly intended to build a co-grouping of four or more
* contributing stages. For up to three stages, prefer the direct {@code
* stage.aggregateN(...)} calls because they offer more static type safety.
*
* @param type of the stream-0 item
* @param type of the grouping key
*/
public class GroupAggregateBuilder {
private final GrAggBuilder graggBuilder;
GroupAggregateBuilder(StageWithGrouping s) {
graggBuilder = new GrAggBuilder<>(s);
}
/**
* Returns the tag corresponding to the pipeline stage this builder
* was obtained from. Use this tag to refer to this stage when building
* the {@code AggregateOperation} that you'll pass to {@link #build
* build(aggrOp)}.
*/
public Tag tag0() {
return Tag.tag0();
}
/**
* 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 {@code AggregateOperation} that you'll pass to
* {@link #build build()}.
*/
@SuppressWarnings("unchecked")
public Tag add(StageWithGrouping stage) {
return graggBuilder.add(stage);
}
/**
* Creates and returns a pipeline stage that performs the
* co-grouping and 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,
* {@code
* StageWithGrouping stage0 = batchStage0.groupingKey(A::key);
* StageWithGrouping stage1 = batchStage1.groupingKey(B::key);
* StageWithGrouping stage2 = batchStage2.groupingKey(C::key);
* StageWithGrouping stage3 = batchStage3.groupingKey(D::key);
*
* AggregateBuilder builder = stage0.aggregateBuilder();
* Tag tagA = builder.tag0();
* Tag tagB = builder.add(stage1, B::key);
* Tag tagC = builder.add(stage2, C::key);
* Tag tagD = builder.add(stage3, D::key);
* BatchStage 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),
* (String key, String result) -> Util.entry(key, result)
* );
* }
*
* @param aggrOp the aggregate operation to perform
* @param the type of items on the stage this builder was obtained from
* @param the type of the output item
* @return a new stage representing the co-aggregation
*/
public BatchStage build(
@Nonnull AggregateOperation aggrOp,
@Nonnull DistributedBiFunction mapToOutputFn
) {
return graggBuilder.buildBatch(aggrOp, mapToOutputFn);
}
/**
* Convenience for {@link #build(AggregateOperation, DistributedBiFunction)
* build(aggrOp, mapToOutputFn)} which emits {@code Map.Entry}s as output.
*
* @param aggrOp the aggregate operation to perform.
* @param the type of items in the pipeline stage this builder was obtained from
* @param the type of the aggregation result
* @return a new stage representing the co-group-and-aggregate operation
*/
public BatchStage> build(
@Nonnull AggregateOperation aggrOp
) {
return graggBuilder.buildBatch(aggrOp, Util::entry);
}
}