CombineFnBase.PerKeyCombineFn (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. After August 12, 2020, you can use unsupported SDKs temporarily while you upgrade your pipelines. For more information, see Using an unsupported SDK.

For information on migrating from the 1.x SDK, see Migrating from Dataflow SDK 1.x for Java.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.transforms

Interface CombineFnBase.PerKeyCombineFn<K,InputT,AccumT,OutputT>

• Type Parameters:

  K - type of keys

  InputT - type of input values

  AccumT - type of mutable accumulator values

  OutputT - type of output values

  All Superinterfaces:

  HasDisplayData, Serializable

  All Known Implementing Classes:

  Combine.KeyedCombineFn, CombineFns.ComposedKeyedCombineFn, CombineFns.ComposedKeyedCombineFnWithContext, CombineWithContext.KeyedCombineFnWithContext

  Enclosing class:

  CombineFnBase

  ---

  
  

  public static interface CombineFnBase.PerKeyCombineFn<K,InputT,AccumT,OutputT>
  extends Serializable, HasDisplayData

  A PerKeyCombineFn<K, InputT, AccumT, OutputT> specifies how to combine a collection of input values of type InputT, associated with a key of type K, into a single output value of type OutputT. It does this via one or more intermediate mutable accumulator values of type AccumT.

  Do not implement this interface directly. Extends Combine.KeyedCombineFn and CombineWithContext.KeyedCombineFnWithContext instead.

• • Method Summary

    All Methods Instance Methods Abstract Methods 

    Modifier and Type	Method and Description
    CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>	forKey(K key, Coder<K> keyCoder) Returns the a regular CombineFnBase.GlobalCombineFn that operates on a specific key.
    Coder<AccumT>	getAccumulatorCoder(CoderRegistry registry, Coder<K> keyCoder, Coder<InputT> inputCoder) Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.
    Coder<OutputT>	getDefaultOutputCoder(CoderRegistry registry, Coder<K> keyCoder, Coder<InputT> inputCoder) Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.

    • Methods inherited from interface com.google.cloud.dataflow.sdk.transforms.display.HasDisplayData

      populateDisplayData

• • Method Detail

    • getAccumulatorCoder

      Coder<AccumT> getAccumulatorCoder(CoderRegistry registry,
                                        Coder<K> keyCoder,
                                        Coder<InputT> inputCoder)
                                 throws CannotProvideCoderException

      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 K keys and input 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.

      Throws:

      CannotProvideCoderException

    • getDefaultOutputCoder

      Coder<OutputT> getDefaultOutputCoder(CoderRegistry registry,
                                           Coder<K> keyCoder,
                                           Coder<InputT> inputCoder)
                                    throws CannotProvideCoderException

      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 K keys and input InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for OutputT values.

      Throws:

      CannotProvideCoderException

    • forKey

      CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT> forKey(K key,
                                                                  Coder<K> keyCoder)

      Returns the a regular CombineFnBase.GlobalCombineFn that operates on a specific key.