org.apache.beam.sdk.transforms

Interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>

Type Parameters:

InputT - type of input values

AccumT - type of mutable accumulator values

OutputT - type of output values

All Superinterfaces:

HasDisplayData, java.io.Serializable

All Known Implementing Classes:

ApproximateDistinct.ApproximateDistinctFn, ApproximateQuantiles.ApproximateQuantilesCombineFn, ApproximateUnique.ApproximateUniqueCombineFn, Combine.AccumulatingCombineFn, Combine.BinaryCombineDoubleFn, Combine.BinaryCombineFn, Combine.BinaryCombineIntegerFn, Combine.BinaryCombineLongFn, Combine.CombineFn, Combine.IterableCombineFn, Combine.SimpleCombineFn, CombineFns.ComposedCombineFn, CombineFns.ComposedCombineFnWithContext, CombineWithContext.CombineFnWithContext, CovarianceFn, Sample.FixedSizedSampleFn, SketchFrequencies.CountMinSketchFn, TDigestQuantiles.TDigestQuantilesFn, Top.TopCombineFn, VarianceFn

Enclosing class:

CombineFnBase

@Internal
public static interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>
extends java.io.Serializable, HasDisplayData

For internal use only; no backwards-compatibility guarantees.

A GloballyCombineFn<InputT, AccumT, OutputT> specifies how to combine a collection of input values of type InputT 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.CombineFn and CombineWithContext.CombineFnWithContext instead.

Method Summary

Modifier and Type	Method and Description
OutputT	defaultValue() Returns the default value when there are no values added to the accumulator.
Coder<AccumT>	getAccumulatorCoder(CoderRegistry registry, 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<InputT> inputCoder) Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.
java.lang.String	getIncompatibleGlobalWindowErrorMessage() Returns the error message for not supported default values in Combine.globally().

Methods inherited from interface org.apache.beam.sdk.transforms.display.HasDisplayData

populateDisplayData

Method Detail

getAccumulatorCoder

Coder<AccumT> getAccumulatorCoder(CoderRegistry registry,
                                  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 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<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 input InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for OutputT values.

Throws:

CannotProvideCoderException

getIncompatibleGlobalWindowErrorMessage

java.lang.String getIncompatibleGlobalWindowErrorMessage()

Returns the error message for not supported default values in Combine.globally().

defaultValue

OutputT defaultValue()

Returns the default value when there are no values added to the accumulator.