com.google.cloud.dataflow.sdk.transforms

Class Combine.BinaryCombineFn<V>

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn<V,Combine.Holder<V>,V>

com.google.cloud.dataflow.sdk.transforms.Combine.BinaryCombineFn<V>

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

Max.MaxFn, Min.MinFn

Enclosing class:

Combine

public abstract static class Combine.BinaryCombineFn<V>
extends Combine.CombineFn<V,Combine.Holder<V>,V>

An abstract subclass of Combine.CombineFn for implementing combiners that are more easily expressed as binary operations.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
BinaryCombineFn()

Method Summary

Modifier and Type	Method and Description
Combine.Holder<V>	addInput(Combine.Holder<V> accumulator, V input) Adds the given input value to the given accumulator, returning the new accumulator value.
abstract V	apply(V left, V right) Applies the binary operation to the two operands, returning the result.
Combine.Holder<V>	createAccumulator() Returns a new, mutable accumulator value, representing the accumulation of zero input values.
V	extractOutput(Combine.Holder<V> accumulator) Returns the output value that is the result of combining all the input values represented by the given accumulator.
Coder<Combine.Holder<V>>	getAccumulatorCoder(CoderRegistry registry, Coder<V> inputCoder) Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.
Coder<V>	getDefaultOutputCoder(CoderRegistry registry, Coder<V> inputCoder) Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.
V	identity() Returns the value that should be used for the combine of the empty set.
Combine.Holder<V>	mergeAccumulators(Iterable<Combine.Holder<V>> accumulators) Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.

Methods inherited from class com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn

apply, asKeyedFn, getOutputType

Methods inherited from class java.lang.Object

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

Constructor Detail

BinaryCombineFn

public BinaryCombineFn()

Method Detail

apply

public abstract V apply(V left,
                        V right)

Applies the binary operation to the two operands, returning the result.

identity

public V identity()

Returns the value that should be used for the combine of the empty set.

createAccumulator

public Combine.Holder<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,Combine.Holder<V>,V>

addInput

public Combine.Holder<V> addInput(Combine.Holder<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,Combine.Holder<V>,V>

mergeAccumulators

public Combine.Holder<V> mergeAccumulators(Iterable<Combine.Holder<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,Combine.Holder<V>,V>

extractOutput

public V extractOutput(Combine.Holder<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,Combine.Holder<V>,V>

getAccumulatorCoder

public Coder<Combine.Holder<V>> getAccumulatorCoder(CoderRegistry registry,
                                                    Coder<V> inputCoder)

Description copied from class: Combine.CombineFn

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.

Overrides:

getAccumulatorCoder in class Combine.CombineFn<V,Combine.Holder<V>,V>

getDefaultOutputCoder

public Coder<V> getDefaultOutputCoder(CoderRegistry registry,
                                      Coder<V> inputCoder)

Description copied from class: Combine.CombineFn

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.

Overrides:

getDefaultOutputCoder in class Combine.CombineFn<V,Combine.Holder<V>,V>