Java Keys類代碼示例

import org.apache.beam.sdk.transforms.Keys; //導入依賴的package包/類
/** Test that the example runs. */
@Test
@Category(ValidatesRunner.class)
public void testTfIdf() throws Exception {

  pipeline.getCoderRegistry().registerCoderForClass(URI.class, StringDelegateCoder.of(URI.class));

  PCollection<KV<String, KV<URI, Double>>> wordToUriAndTfIdf = pipeline
      .apply(Create.of(
          KV.of(new URI("x"), "a b c d"),
          KV.of(new URI("y"), "a b c"),
          KV.of(new URI("z"), "a m n")))
      .apply(new TfIdf.ComputeTfIdf());

  PCollection<String> words = wordToUriAndTfIdf
      .apply(Keys.<String>create())
      .apply(Distinct.<String>create());

  PAssert.that(words).containsInAnyOrder(Arrays.asList("a", "m", "n", "b", "c", "d"));

  pipeline.run().waitUntilFinish();
}
 

import org.apache.beam.sdk.transforms.Keys; //導入依賴的package包/類
@Test
public void traverseMultipleTimesThrows() {
  p.apply(
          Create.of(KV.of(1, (Void) null), KV.of(2, (Void) null), KV.of(3, (Void) null))
              .withCoder(KvCoder.of(VarIntCoder.of(), VoidCoder.of())))
      .apply(GroupByKey.<Integer, Void>create())
      .apply(Keys.<Integer>create());

  p.traverseTopologically(visitor);
  thrown.expect(IllegalStateException.class);
  thrown.expectMessage("already been finalized");
  thrown.expectMessage(KeyedPValueTrackingVisitor.class.getSimpleName());
  p.traverseTopologically(visitor);
}
 

import org.apache.beam.sdk.transforms.Keys; //導入依賴的package包/類
/**
 * Basic use of the LazyAvroCoder with the default schema supplier.
 */
@Test
public void testBasic() {
    // Create a PCollection of simple records, and assign it to be encoded with a LazyAvroCoder.
    PCollection<IndexedRecord> a = p.apply("a", RowGeneratorIO.read().withSchema(SampleSchemas.recordSimple()));
    a.setCoder(LazyAvroCoder.of());

    // Construct the a job looks like (a and c are collections of IndexedRecords):
    //
    // a ----> b ----> c ----> d
    // |
    // \-> b2

    // Trigger a transformation that requires the data to be shuffled and run the pipelne.
    PCollection<KV<IndexedRecord, Long>> b = a.apply("b", Count.<IndexedRecord> perElement());
    PCollection<IndexedRecord> c = b.apply("c", Keys.<IndexedRecord> create());
    c.setCoder(LazyAvroCoder.of());
    PCollection<KV<IndexedRecord, Long>> d = c.apply("d", Count.<IndexedRecord> perElement());

    PCollection<KV<IndexedRecord, Long>> b2 = a.apply("b2", Count.<IndexedRecord> perElement());

    p.run().waitUntilFinish();

    // No exception should have occurred.

    assertThat(LazyAvroCoder.StaticSchemaHolderSupplier.getSchemas(), hasSize(2));
    assertThat(LazyAvroCoder.StaticSchemaHolderSupplier.getSchemas(),
            contains(SampleSchemas.recordSimple(), SampleSchemas.recordSimple()));

    // Check that the reset cleans the supplier.
    LazyAvroCoder.resetSchemaSupplier();
    assertThat(LazyAvroCoder.StaticSchemaHolderSupplier.getSchemas(), emptyIterable());
}
 

import org.apache.beam.sdk.transforms.Keys; //導入依賴的package包/類
/**
 * Exactly the same test as {@link #testBasic()} but reusing the LazyAvroCoder.
 */
@Test
public void testBasicReuse() {
    LazyAvroCoder lac = LazyAvroCoder.of();

    // Create a PCollection of simple records, and assign it to be encoded with a LazyAvroCoder.
    PCollection<IndexedRecord> a = p.apply("a", RowGeneratorIO.read().withSchema(SampleSchemas.recordSimple()));
    a.setCoder(lac);

    // Construct the a job looks like (a and c are collections of IndexedRecords):
    //
    // a ----> b ----> c ----> d
    // |
    // \-> b2

    // Trigger a transformation that requires the data to be shuffled and run the pipelne.
    PCollection<KV<IndexedRecord, Long>> b = a.apply("b", Count.<IndexedRecord> perElement());
    PCollection<IndexedRecord> c = b.apply("c", Keys.<IndexedRecord> create());
    c.setCoder(lac);
    PCollection<KV<IndexedRecord, Long>> d = c.apply("d", Count.<IndexedRecord> perElement());

    PCollection<KV<IndexedRecord, Long>> b2 = a.apply("b2", Count.<IndexedRecord> perElement());

    p.run().waitUntilFinish();

    // No exception should have occurred.

    // Only one schema was registered.
    assertThat(LazyAvroCoder.StaticSchemaHolderSupplier.getSchemas(), hasSize(1));
    assertThat(LazyAvroCoder.StaticSchemaHolderSupplier.getSchemas(), contains(SampleSchemas.recordSimple()));
}
 

import org.apache.beam.sdk.transforms.Keys; //導入依賴的package包/類
@Override
public PCollection<T> expand(PCollection<T> input) {
  return input
      .apply("Break fusion mapper", ParDo.of(new DummyMapFn<T>()))
      .apply(GroupByKey.<T, Integer>create())
      .apply(Keys.<T>create());
}