Combine.IterableCombineFn (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

com.google.cloud.dataflow.sdk.transforms

Class Combine.IterableCombineFn<V>

    • Method Detail

      • 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.
      • 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.

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

        Specified by:
        addInput in class Combine.CombineFn<V,List<V>,V>
      • 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.

        May modify any of the argument accumulators. May return a fresh accumulator, or may return one of the (modified) argument accumulators.

        Specified by:
        mergeAccumulators in class Combine.CombineFn<V,List<V>,V>
      • 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:
        HasDisplayData
      • getAccumulatorCoder

        public Coder<AccumT> getAccumulatorCoder(CoderRegistry registry,
                                                 Coder<InputT> 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


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