com.google.cloud.dataflow.sdk.transforms

Class Top.TopCombineFn<T,ComparatorT extends Comparator<T> & Serializable>

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn<InputT,AccumT,OutputT>

com.google.cloud.dataflow.sdk.transforms.Combine.AccumulatingCombineFn<T,com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT>,List<T>>

com.google.cloud.dataflow.sdk.transforms.Top.TopCombineFn<T,ComparatorT>

Type Parameters:

T - type of element being compared

All Implemented Interfaces:

Serializable

Enclosing class:

Top

public static class Top.TopCombineFn<T,ComparatorT extends Comparator<T> & Serializable>
extends Combine.AccumulatingCombineFn<T,com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT>,List<T>>

CombineFn for Top transforms that combines a bunch of Ts into a single count-long List<T>, using compareFn to choose the largest Ts.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class com.google.cloud.dataflow.sdk.transforms.Combine.AccumulatingCombineFn

Combine.AccumulatingCombineFn.Accumulator<InputT,AccumT,OutputT>

Constructor Summary

Constructors

Constructor and Description
TopCombineFn(int count, ComparatorT compareFn)

Method Summary

Modifier and Type	Method and Description
com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT>	createAccumulator() Returns a new, mutable accumulator value, representing the accumulation of zero input values.
Coder<com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT>>	getAccumulatorCoder(CoderRegistry registry, Coder<T> inputCoder) Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.

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

addInput, extractOutput, mergeAccumulators

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

apply, asKeyedFn, getDefaultOutputCoder, getOutputType

Methods inherited from class java.lang.Object

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

Constructor Detail

TopCombineFn

public TopCombineFn(int count,
                    ComparatorT compareFn)

Method Detail

createAccumulator

public com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT> 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<T,com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT extends Comparator<T> & Serializable>,List<T>>

getAccumulatorCoder

public Coder<com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT>> getAccumulatorCoder(CoderRegistry registry,
                                                                                                          Coder<T> 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<T,com.google.cloud.dataflow.sdk.transforms.Top.BoundedHeap<T,ComparatorT extends Comparator<T> & Serializable>,List<T>>