org.apache.beam.sdk.transforms

Class Combine.IterableCombineFn<V>

java.lang.Object

org.apache.beam.sdk.transforms.Combine.CombineFn<V,java.util.List<V>,V>

org.apache.beam.sdk.transforms.Combine.IterableCombineFn<V>

All Implemented Interfaces:

java.io.Serializable, CombineFnBase.GlobalCombineFn<V,java.util.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,java.util.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:

Serialized Form

Method Summary

Modifier and Type	Method and Description
java.util.List<V>	addInput(java.util.List<V> accumulator, V input) Adds the given input value to the given accumulator, returning the new accumulator value.
java.util.List<V>	compact(java.util.List<V> accumulator) Returns an accumulator that represents the same logical value as the input accumulator, but may have a more compact representation.
java.util.List<V>	createAccumulator() Returns a new, mutable accumulator value, representing the accumulation of zero input values.
V	extractOutput(java.util.List<V> accumulator) Returns the output value that is the result of combining all the input values represented by the given accumulator.
java.lang.reflect.TypeVariable<?>	getAccumTVariable() Returns the TypeVariable of AccumT.
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().
java.lang.reflect.TypeVariable<?>	getInputTVariable() Returns the TypeVariable of InputT.
java.lang.String	getNameOverride()
java.lang.reflect.TypeVariable<?>	getOutputTVariable() Returns the TypeVariable of OutputT.
java.util.List<V>	mergeAccumulators(java.lang.Iterable<java.util.List<V>> accumulators) Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.
static <V> Combine.IterableCombineFn<V>	of(SerializableFunction<java.lang.Iterable<V>,V> combiner) Returns a CombineFn that uses the given SerializableFunction to combine values.
static <V> Combine.IterableCombineFn<V>	of(SerializableFunction<java.lang.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.
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.

Methods inherited from class org.apache.beam.sdk.transforms.Combine.CombineFn

apply, defaultValue, getInputType, getOutputType

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

of

public static <V> Combine.IterableCombineFn<V> of(SerializableFunction<java.lang.Iterable<V>,V> combiner)

Returns a CombineFn that uses the given SerializableFunction to combine values.

of

public static <V> Combine.IterableCombineFn<V> of(SerializableFunction<java.lang.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 java.util.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,java.util.List<V>,V>

addInput

public java.util.List<V> addInput(java.util.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,java.util.List<V>,V>

Parameters:

accumulator - may be modified and returned for efficiency

input - should not be mutated

mergeAccumulators

public java.util.List<V> mergeAccumulators(java.lang.Iterable<java.util.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,java.util.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(java.util.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,java.util.List<V>,V>

Parameters:

accumulator - can be modified for efficiency

compact

public java.util.List<V> compact(java.util.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,java.util.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

getNameOverride

public java.lang.String getNameOverride()

Specified by:

getNameOverride in interface org.apache.beam.sdk.util.NameUtils.NameOverride

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

getDefaultOutputCoder

public Coder<OutputT> getDefaultOutputCoder(CoderRegistry registry,
                                            Coder<InputT> 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 java.lang.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 java.lang.reflect.TypeVariable<?> getInputTVariable()

Returns the TypeVariable of InputT.

getAccumTVariable

public java.lang.reflect.TypeVariable<?> getAccumTVariable()

Returns the TypeVariable of AccumT.

getOutputTVariable

public java.lang.reflect.TypeVariable<?> getOutputTVariable()

Returns the TypeVariable of OutputT.