InputT - type of input valuesOutputT - type of output valuespublic static class Combine.GloballyAsSingletonView<InputT,OutputT> extends PTransform<PCollection<InputT>,PCollectionView<OutputT>>
Combine.GloballyAsSingletonView<InputT, OutputT> takes a PCollection<InputT>
and returns a PCollectionView<OutputT> whose elements are the result of combining all
the elements in each window of the input PCollection, using a specified CombineFn<InputT, AccumT, OutputT>. 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<Integer> pc = ...;
PCollection<Integer> sum = pc.apply(
Combine.globally(new Sum.SumIntegerFn()));
Combining can happen in parallel, with different subsets of the input PCollection
being combined separately, and their intermediate results combined further, in an arbitrary
tree reduction pattern, until a single result value is produced.
If a value is requested from the view for a window that is not present and insertDefault is true, the result of calling the CombineFn on empty input will
returned. If insertDefault is false, an exception will be thrown instead.
By default, the Coder of the output PValue<OutputT> is inferred from the
concrete type of the CombineFn<InputT, AccumT, OutputT>'s output type OutputT.
See also Combine.perKey(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.PerKey and Combine.groupedValues(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.GroupedValues, which are useful for combining values associated with
each key in a PCollection of KVs.
annotations, name, resourceHints| Modifier and Type | Method and Description |
|---|---|
PCollectionView<OutputT> |
expand(PCollection<InputT> input)
Override this method to specify how this
PTransform should be expanded on the given
InputT. |
CombineFnBase.GlobalCombineFn<? super InputT,?,OutputT> |
getCombineFn() |
int |
getFanout() |
boolean |
getInsertDefault() |
void |
populateDisplayData(DisplayData.Builder builder)
Register display data for the given transform or component.
|
addAnnotation, compose, compose, getAdditionalInputs, getAnnotations, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, setResourceHints, toString, validate, validatepublic PCollectionView<OutputT> expand(PCollection<InputT> input)
PTransformPTransform 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).
expand in class PTransform<PCollection<InputT>,PCollectionView<OutputT>>public int getFanout()
public boolean getInsertDefault()
public CombineFnBase.GlobalCombineFn<? super InputT,?,OutputT> getCombineFn()
public void populateDisplayData(DisplayData.Builder builder)
PTransformpopulateDisplayData(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.
populateDisplayData in interface HasDisplayDatapopulateDisplayData in class PTransform<PCollection<InputT>,PCollectionView<OutputT>>builder - The builder to populate with display data.HasDisplayData