org.apache.beam.runners.samza.translation.SamzaPublishViewTransformOverride.java Source code

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Here is the source code for org.apache.beam.runners.samza.translation.SamzaPublishViewTransformOverride.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.beam.runners.samza.translation;

import com.google.common.collect.Iterables;
import java.util.ArrayList;
import java.util.List;
import org.apache.beam.runners.core.construction.SingleInputOutputOverrideFactory;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.CoderRegistry;
import org.apache.beam.sdk.coders.ListCoder;
import org.apache.beam.sdk.runners.AppliedPTransform;
import org.apache.beam.sdk.transforms.Combine;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.View;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionView;

/** Samza override for {@link View} (side input) transforms. */
class SamzaPublishViewTransformOverride<ElemT, ViewT> extends
        SingleInputOutputOverrideFactory<PCollection<ElemT>, PCollection<ElemT>, View.CreatePCollectionView<ElemT, ViewT>> {
    @Override
    public PTransformReplacement<PCollection<ElemT>, PCollection<ElemT>> getReplacementTransform(
            AppliedPTransform<PCollection<ElemT>, PCollection<ElemT>, View.CreatePCollectionView<ElemT, ViewT>> transform) {

        @SuppressWarnings("unchecked")
        PCollection<ElemT> input = (PCollection<ElemT>) Iterables.getOnlyElement(transform.getInputs().values());

        return PTransformReplacement.of(input,
                new SamzaCreatePCollectionViewTransform<>(transform.getTransform().getView()));
    }

    private static class SamzaCreatePCollectionViewTransform<ElemT, ViewT>
            extends PTransform<PCollection<ElemT>, PCollection<ElemT>> {
        private final PCollectionView<ViewT> view;

        public SamzaCreatePCollectionViewTransform(PCollectionView<ViewT> view) {
            this.view = view;
        }

        @Override
        public PCollection<ElemT> expand(PCollection<ElemT> input) {
            // This actually creates a branch in the graph that publishes the view but then returns
            // the original input. This is copied from the Flink runner.
            input.apply(Combine.globally(new Concatenate<ElemT>()).withoutDefaults())
                    .apply(new SamzaPublishView<>(view));
            return input;
        }
    }

    private static class Concatenate<T> extends Combine.CombineFn<T, List<T>, List<T>> {
        @Override
        public List<T> createAccumulator() {
            return new ArrayList<>();
        }

        @Override
        public List<T> addInput(List<T> accumulator, T input) {
            accumulator.add(input);
            return accumulator;
        }

        @Override
        public List<T> mergeAccumulators(Iterable<List<T>> accumulators) {
            List<T> result = createAccumulator();
            for (List<T> accumulator : accumulators) {
                result.addAll(accumulator);
            }
            return result;
        }

        @Override
        public List<T> extractOutput(List<T> accumulator) {
            return accumulator;
        }

        @Override
        public Coder<List<T>> getAccumulatorCoder(CoderRegistry registry, Coder<T> inputCoder) {
            return ListCoder.of(inputCoder);
        }

        @Override
        public Coder<List<T>> getDefaultOutputCoder(CoderRegistry registry, Coder<T> inputCoder) {
            return ListCoder.of(inputCoder);
        }
    }
}