Google Cloud Dataflow SDK for Java, version 1.9.1
Class Keys<K>
- java.lang.Object
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- com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<? extends KV<K,?>>,PCollection<K>>
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- com.google.cloud.dataflow.sdk.transforms.Keys<K>
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- Type Parameters:
K
- the type of the keys in the inputPCollection
, and the type of the elements in the outputPCollection
- All Implemented Interfaces:
- HasDisplayData, Serializable
public class Keys<K> extends PTransform<PCollection<? extends KV<K,?>>,PCollection<K>>
Keys<K>
takes aPCollection
ofKV<K, V>
s and returns aPCollection<K>
of the keys.Example of use:
PCollection<KV<String, Long>> wordCounts = ...; PCollection<String> words = wordCounts.apply(Keys.<String>create());
Each output element has the same timestamp and is in the same windows as its corresponding input element, and the output
PCollection
has the sameWindowFn
associated with it as the input.See also
Values
.- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform
name
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method and Description PCollection<K>
apply(PCollection<? extends KV<K,?>> in)
Applies thisPTransform
on the givenInputT
, and returns itsOutput
.static <K> Keys<K>
create()
Returns aKeys<K>
PTransform
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Methods inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform
getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, populateDisplayData, toString, validate
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Method Detail
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create
public static <K> Keys<K> create()
Returns aKeys<K>
PTransform
.- Type Parameters:
K
- the type of the keys in the inputPCollection
, and the type of the elements in the outputPCollection
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apply
public PCollection<K> apply(PCollection<? extends KV<K,?>> in)
Description copied from class:PTransform
Applies thisPTransform
on the givenInputT
, and returns itsOutput
.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).
The default implementation throws an exception. A derived class must either implement apply, or else each runner must supply a custom implementation via
PipelineRunner.apply(com.google.cloud.dataflow.sdk.transforms.PTransform<InputT, OutputT>, InputT)
.- Overrides:
apply
in classPTransform<PCollection<? extends KV<K,?>>,PCollection<K>>
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