content: /*
   * 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.
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  package org.apache.beam.runners.spark.structuredstreaming.translation.batch;
  
  import static org.apache.beam.runners.spark.structuredstreaming.translation.utils.ScalaInterop.fun1;
  
  import java.util.Collection;
  import java.util.Iterator;
  import org.apache.beam.runners.spark.structuredstreaming.translation.TransformTranslator;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.transforms.Flatten;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionList;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableList;
  import org.apache.spark.sql.Dataset;
  import org.apache.spark.sql.Encoder;
  
  class FlattenTranslatorBatch<T>
      extends TransformTranslator<PCollectionList<T>, PCollection<T>, Flatten.PCollections<T>> {
  
    FlattenTranslatorBatch() {
      super(0.1f);
    }
  
    @Override
    public void translate(Flatten.PCollections<T> transform, Context cxt) {
      Collection<PCollection<?>> pCollections = cxt.getInputs().values();
      Coder<T> outputCoder = cxt.getOutput().getCoder();
      Encoder<WindowedValue<T>> outputEnc =
          cxt.windowedEncoder(outputCoder, windowCoder(cxt.getOutput()));
  
      Dataset<WindowedValue<T>> result;
      Iterator<PCollection<T>> pcIt = (Iterator) pCollections.iterator();
      if (pcIt.hasNext()) {
        result = getDataset(pcIt.next(), outputCoder, outputEnc, cxt);
        while (pcIt.hasNext()) {
          result = result.union(getDataset(pcIt.next(), outputCoder, outputEnc, cxt));
        }
      } else {
        result = cxt.createDataset(ImmutableList.of(), outputEnc);
      }
      cxt.putDataset(cxt.getOutput(), result);
    }
  
    private Dataset<WindowedValue<T>> getDataset(
        PCollection<T> pc, Coder<T> coder, Encoder<WindowedValue<T>> enc, Context cxt) {
      Dataset<WindowedValue<T>> current = cxt.getDataset(pc);
      // if coders don't match, map using identity function to replace encoder
      return pc.getCoder().equals(coder) ? current : current.map(fun1(v -> v), enc);
    }
  }
  