org.apache.beam.runners.direct.ParDoSingleViaMultiOverrideFactory.java Source code

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Here is the source code for org.apache.beam.runners.direct.ParDoSingleViaMultiOverrideFactory.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.direct;

import com.google.common.collect.Iterables;
import java.util.List;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.runners.PTransformOverrideFactory;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.ParDo.Bound;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionTuple;
import org.apache.beam.sdk.values.TaggedPValue;
import org.apache.beam.sdk.values.TupleTag;
import org.apache.beam.sdk.values.TupleTagList;

/**
 * A {@link PTransformOverrideFactory} that overrides single-output {@link ParDo} to implement
 * it in terms of multi-output {@link ParDo}.
 */
class ParDoSingleViaMultiOverrideFactory<InputT, OutputT> implements
        PTransformOverrideFactory<PCollection<? extends InputT>, PCollection<OutputT>, Bound<InputT, OutputT>> {
    @Override
    public PTransform<PCollection<? extends InputT>, PCollection<OutputT>> getReplacementTransform(
            Bound<InputT, OutputT> transform) {
        return new ParDoSingleViaMulti<>(transform);
    }

    @Override
    public PCollection<? extends InputT> getInput(List<TaggedPValue> inputs, Pipeline p) {
        return (PCollection<? extends InputT>) Iterables.getOnlyElement(inputs).getValue();
    }

    static class ParDoSingleViaMulti<InputT, OutputT>
            extends PTransform<PCollection<? extends InputT>, PCollection<OutputT>> {
        private static final String MAIN_OUTPUT_TAG = "main";

        private final ParDo.Bound<InputT, OutputT> underlyingParDo;

        public ParDoSingleViaMulti(ParDo.Bound<InputT, OutputT> underlyingParDo) {
            this.underlyingParDo = underlyingParDo;
        }

        @Override
        public PCollection<OutputT> expand(PCollection<? extends InputT> input) {

            // Output tags for ParDo need only be unique up to applied transform
            TupleTag<OutputT> mainOutputTag = new TupleTag<OutputT>(MAIN_OUTPUT_TAG);

            PCollectionTuple outputs = input
                    .apply(ParDo.of(underlyingParDo.getFn()).withSideInputs(underlyingParDo.getSideInputs())
                            .withOutputTags(mainOutputTag, TupleTagList.empty()));
            PCollection<OutputT> output = outputs.get(mainOutputTag);

            output.setTypeDescriptor(underlyingParDo.getFn().getOutputTypeDescriptor());
            return output;
        }
    }
}