org.apache.beam.sdk.transforms

Class Combine.GroupedValues<K,InputT,OutputT>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

org.apache.beam.sdk.transforms.Combine.GroupedValues<K,InputT,OutputT>

Type Parameters:

K - type of input and output keys

InputT - type of input values

OutputT - type of output values

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

Enclosing class:

Combine

public static class Combine.GroupedValues<K,InputT,OutputT>
extends PTransform<PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

GroupedValues<K, InputT, OutputT> takes a PCollection<KV<K, Iterable<InputT>>>, such as the result of GroupByKey, applies a specified CombineFn<InputT, AccumT, OutputT> to each of the input KV<K, Iterable<InputT>> elements to produce a combined output KV<K, OutputT> element, and returns a PCollection<KV<K, OutputT>> containing all the combined output elements. It is common for InputT == OutputT, but not required. Common combining functions include sums, mins, maxes, and averages of numbers, conjunctions and disjunctions of booleans, statistical aggregations, etc.

Example of use:

 PCollection<KV<String, Integer>> pc = ...;
 PCollection<KV<String, Iterable<Integer>>> groupedByKey = pc.apply(
     new GroupByKey<String, Integer>());
 PCollection<KV<String, Integer>> sumByKey = groupedByKey.apply(
     Combine.<String, Integer>groupedValues(
         new Sum.SumIntegerFn()));
 
 

See also Combine.perKey(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.PerKey, which captures the common pattern of "combining by key" in a single easy-to-use PTransform.

Combining for different keys can happen in parallel. Moreover, combining of the Iterable<InputT> values associated a single key can happen in parallel, with different subsets of the values being combined separately, and their intermediate results combined further, in an arbitrary tree reduction pattern, until a single result value is produced for each key.

By default, the Coder of the keys of the output PCollection<KV<K, OutputT>> is that of the keys of the input PCollection<KV<K, InputT>>, and the Coder of the values of the output PCollection<KV<K, OutputT>> is inferred from the concrete type of the CombineFn<InputT, AccumT, OutputT>'s output type OutputT.

Each output element has the same timestamp and is in the same window as its corresponding input element, and the output PCollection has the same WindowFn associated with it as the input.

See also Combine.globally(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.Globally, which combines all the values in a PCollection into a single value in a PCollection.

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.PTransform

name

Method Summary

Modifier and Type	Method and Description
PCollection<KV<K,OutputT>>	expand(PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>> input) Override this method to specify how this PTransform should be expanded on the given InputT.
org.apache.beam.sdk.util.AppliedCombineFn<? super K,? super InputT,?,OutputT>	getAppliedFn(CoderRegistry registry, Coder<? extends KV<K,? extends java.lang.Iterable<InputT>>> inputCoder, WindowingStrategy<?,?> windowingStrategy) Returns the Combine.CombineFn bound to its coders.
Coder<KV<K,OutputT>>	getDefaultOutputCoder(PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>> input) Returns the default Coder to use for the output of this single-output PTransform when applied to the given input.
CombineFnBase.GlobalCombineFn<? super InputT,?,OutputT>	getFn() Returns the CombineFnBase.GlobalCombineFn used by this Combine operation.
java.util.List<PCollectionView<?>>	getSideInputs()
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
Combine.GroupedValues<K,InputT,OutputT>	withSideInputs(java.lang.Iterable<? extends PCollectionView<?>> sideInputs)
Combine.GroupedValues<K,InputT,OutputT>	withSideInputs(PCollectionView<?>... sideInputs)

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, toString, validate

Methods inherited from class java.lang.Object

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

Method Detail

withSideInputs

public Combine.GroupedValues<K,InputT,OutputT> withSideInputs(PCollectionView<?>... sideInputs)

withSideInputs

public Combine.GroupedValues<K,InputT,OutputT> withSideInputs(java.lang.Iterable<? extends PCollectionView<?>> sideInputs)

getFn

public CombineFnBase.GlobalCombineFn<? super InputT,?,OutputT> getFn()

Returns the CombineFnBase.GlobalCombineFn used by this Combine operation.

getSideInputs

public java.util.List<PCollectionView<?>> getSideInputs()

expand

public PCollection<KV<K,OutputT>> expand(PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>> input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

Specified by:

expand in class PTransform<PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

getAppliedFn

public org.apache.beam.sdk.util.AppliedCombineFn<? super K,? super InputT,?,OutputT> getAppliedFn(CoderRegistry registry,
                                                                                                  Coder<? extends KV<K,? extends java.lang.Iterable<InputT>>> inputCoder,
                                                                                                  WindowingStrategy<?,?> windowingStrategy)

Returns the Combine.CombineFn bound to its coders.

For internal use.

getDefaultOutputCoder

public Coder<KV<K,OutputT>> getDefaultOutputCoder(PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>> input)
                                           throws CannotProvideCoderException

Description copied from class: PTransform

Returns the default Coder to use for the output of this single-output PTransform when applied to the given input.

By default, always throws.

Overrides:

getDefaultOutputCoder in class PTransform<PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

Throws:

CannotProvideCoderException - if none can be inferred.

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: PTransform

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

Overrides:

populateDisplayData in class PTransform<PCollection<? extends KV<K,? extends java.lang.Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData