GenerateShardedTable.java

/*
* Licensed to the Apache Software Foundation (ASF) under one
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* 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
*
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* See the License for the specific language governing permissions and
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package org.apache.beam.sdk.io.gcp.bigquery;

import com.google.api.services.bigquery.model.TableRow;
import java.io.IOException;
import java.util.concurrent.ThreadLocalRandom;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.values.KV;

/**
 * Given a write to a specific table, assign that to one of the
 * {@link GenerateShardedTable#numShards} keys assigned to that table.
 */
class GenerateShardedTable extends DoFn<KV<TableDestination, TableRow>,
    KV<ShardedKey<String>, TableRow>> {
  private final int numShards;

  GenerateShardedTable(int numShards) {
    this.numShards = numShards;
  }

  @ProcessElement
  public void processElement(ProcessContext context, BoundedWindow window) throws IOException {
    ThreadLocalRandom randomGenerator = ThreadLocalRandom.current();
    // We output on keys 0-numShards.
    String tableSpec = context.element().getKey().getTableSpec();
    context.output(KV.of(ShardedKey.of(tableSpec, randomGenerator.nextInt(0, numShards)),
        context.element().getValue()));
  }
}