Package org.apache.beam.sdk.transforms

Class Combine.IterableCombineFn<V>

java.lang.Object
org.apache.beam.sdk.transforms.Combine.CombineFn<V,List<V>,V>
org.apache.beam.sdk.transforms.Combine.IterableCombineFn<V>
All Implemented Interfaces:
Serializable, CombineFnBase.GlobalCombineFn<V,List<V>,V>, HasDisplayData, org.apache.beam.sdk.util.NameUtils.NameOverride
Direct Known Subclasses:
Combine.SimpleCombineFn
Enclosing class:
Combine
public static class Combine.IterableCombineFn<V> extends Combine.CombineFn<V,List<V>,V> implements org.apache.beam.sdk.util.NameUtils.NameOverride
Converts a SerializableFunction from Iterable<V>s to Vs into a simple Combine.CombineFn over Vs.

Used in the implementation of convenience methods like Combine.globally(SerializableFunction), Combine.perKey(SerializableFunction), and Combine.groupedValues(SerializableFunction).

See Also:

  • Method Details

    • of

      public static <V> Combine.IterableCombineFn<V> of(SerializableFunction<Iterable<V>,V> combiner)
      Returns a CombineFn that uses the given SerializableFunction to combine values.

    • of

      public static <V> Combine.IterableCombineFn<V> of(SerializableFunction<Iterable<V>,V> combiner, int bufferSize)
      Returns a CombineFn that uses the given SerializableFunction to combine values, attempting to buffer at least bufferSize values between invocations.

    • createAccumulator

      public List<V> createAccumulator()
      Description copied from class: Combine.CombineFn
      Returns a new, mutable accumulator value, representing the accumulation of zero input values.
      Specified by:
      createAccumulator in class Combine.CombineFn<V,List<V>,V>

    • addInput

      public List<V> addInput(List<V> accumulator, V input)
      Description copied from class: Combine.CombineFn
      Adds the given input value to the given accumulator, returning the new accumulator value.
      Specified by:
      addInput in class Combine.CombineFn<V,List<V>,V>
      Parameters:
      accumulator - may be modified and returned for efficiency
      input - should not be mutated

    • mergeAccumulators

      public List<V> mergeAccumulators(Iterable<List<V>> accumulators)
      Description copied from class: Combine.CombineFn
      Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.
      Specified by:
      mergeAccumulators in class Combine.CombineFn<V,List<V>,V>
      Parameters:
      accumulators - only the first accumulator may be modified and returned for efficiency; the other accumulators should not be mutated, because they may be shared with other code and mutating them could lead to incorrect results or data corruption.

    • extractOutput

      public V extractOutput(List<V> accumulator)
      Description copied from class: Combine.CombineFn
      Returns the output value that is the result of combining all the input values represented by the given accumulator.
      Specified by:
      extractOutput in class Combine.CombineFn<V,List<V>,V>
      Parameters:
      accumulator - can be modified for efficiency

    • compact

      public List<V> compact(List<V> accumulator)
      Description copied from class: Combine.CombineFn
      Returns an accumulator that represents the same logical value as the input accumulator, but may have a more compact representation.

      For most CombineFns this would be a no-op, but should be overridden by CombineFns that (for example) buffer up elements and combine them in batches.

      For efficiency, the input accumulator may be modified and returned.

      By default returns the original accumulator.

      Overrides:
      compact in class Combine.CombineFn<V,List<V>,V>

    • populateDisplayData

      public void populateDisplayData(DisplayData.Builder builder)
      Register display data for the given transform or component.

      populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

      By default, does not register any display data. Implementors may override this method to provide their own display data.

      Specified by:
      populateDisplayData in interface HasDisplayData
      Parameters:
      builder - The builder to populate with display data.
      See Also:

    • getNameOverride

      public String getNameOverride()
      Specified by:
      getNameOverride in interface org.apache.beam.sdk.util.NameUtils.NameOverride

    • getAccumulatorCoder

      public Coder<List<V>> getAccumulatorCoder(CoderRegistry registry, Coder<V> inputCoder) throws CannotProvideCoderException
      Description copied from interface: CombineFnBase.GlobalCombineFn
      Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.

      By default, uses the knowledge of the Coder being used for InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for AccumT values.

      This is the Coder used to send data through a communication-intensive shuffle step, so a compact and efficient representation may have significant performance benefits.

      Specified by:
      getAccumulatorCoder in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>
      Throws:
      CannotProvideCoderException

    • getDefaultOutputCoder

      public Coder<V> getDefaultOutputCoder(CoderRegistry registry, Coder<V> inputCoder) throws CannotProvideCoderException
      Description copied from interface: CombineFnBase.GlobalCombineFn
      Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.

      By default, uses the knowledge of the Coder being used for input InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for OutputT values.

      Specified by:
      getDefaultOutputCoder in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>
      Throws:
      CannotProvideCoderException

    • getIncompatibleGlobalWindowErrorMessage

      public String getIncompatibleGlobalWindowErrorMessage()
      Description copied from interface: CombineFnBase.GlobalCombineFn
      Returns the error message for not supported default values in Combine.globally().
      Specified by:
      getIncompatibleGlobalWindowErrorMessage in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>

    • getInputTVariable

      public TypeVariable<?> getInputTVariable()
      Returns the TypeVariable of InputT.

    • getAccumTVariable

      public TypeVariable<?> getAccumTVariable()
      Returns the TypeVariable of AccumT.

    • getOutputTVariable

      public TypeVariable<?> getOutputTVariable()
      Returns the TypeVariable of OutputT.