org.apache.beam.sdk.transforms

Class MapKeys<K1,K2,V>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<KV<K1,V>>,PCollection<KV<K2,V>>>

org.apache.beam.sdk.transforms.MapKeys<K1,K2,V>

Type Parameters:

K1 - the type of the keys in the input PCollection

K2 - the type of the keys in the output PCollection

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

public class MapKeys<K1,K2,V>
extends PTransform<PCollection<KV<K1,V>>,PCollection<KV<K2,V>>>

MapKeys maps a SerializableFunction<K1,K2> over keys of a PCollection<KV<K1,V>> and returns a PCollection<KV<K2, V>>.

Example of use:

 PCollection<KV<Integer, String>> input = ...;
 PCollection<KV<Double, String> output =
      input.apply(MapKeys.into(TypeDescriptors.doubles()).via(Integer::doubleValue));
 

See also MapValues.

See Also:

Serialized Form

Field Summary

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

name, resourceHints

Method Summary

Modifier and Type	Method and Description
<FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K1,V>,KV<K2,V>,FailureT>	exceptionsInto(TypeDescriptor<FailureT> failureTypeDescriptor) Returns a new SimpleMapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using SimpleMapWithFailures.exceptionsVia(ProcessFunction).
<FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K1,V>,KV<K2,V>,FailureT>	exceptionsVia(InferableFunction<WithFailures.ExceptionElement<KV<K1,V>>,FailureT> exceptionHandler) Returns a new SimpleMapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.
PCollection<KV<K2,V>>	expand(PCollection<KV<K1,V>> input) Override this method to specify how this PTransform should be expanded on the given InputT.
static <K2> MapKeys<?,K2,?>	into(TypeDescriptor<K2> outputType) Returns a new MapKeys transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(SerializableFunction).
<NewValueT,NewKeyT> MapKeys<NewKeyT,K2,NewValueT>	via(SerializableFunction<NewKeyT,K2> fn) Returns a MapKeys<K1, K2, V> PTransform for a ProcessFunction<NewK1, K2> with predefined outputType.

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

compose, compose, getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, populateDisplayData, setResourceHints, toString, validate, validate

Methods inherited from class java.lang.Object

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

Method Detail

via

public <NewValueT,NewKeyT> MapKeys<NewKeyT,K2,NewValueT> via(SerializableFunction<NewKeyT,K2> fn)

Returns a MapKeys<K1, K2, V> PTransform for a ProcessFunction<NewK1, K2> with predefined outputType.

Type Parameters:

NewKeyT - the type of the keys in the input PCollection

NewValueT - the type of the values in the input and output PCollections

into

public static <K2> MapKeys<?,K2,?> into(TypeDescriptor<K2> outputType)

Returns a new MapKeys transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(SerializableFunction).

exceptionsInto

@RequiresNonNull(value="fn")
public <FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K1,V>,KV<K2,V>,FailureT> exceptionsInto(TypeDescriptor<FailureT> failureTypeDescriptor)

Returns a new SimpleMapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using SimpleMapWithFailures.exceptionsVia(ProcessFunction).

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

Example usage:

 Result<PCollection<KV<Integer, String>>, String> result =
         input.apply(
             MapKeys.into(TypeDescriptors.integers())
                 .<String, String>via(word -> 1 / word.length)  // Could throw ArithmeticException
                 .exceptionsInto(TypeDescriptors.strings())
                 .exceptionsVia(ee -> ee.exception().getMessage()));
 PCollection<KV<Integer, String>> output = result.output();
 PCollection<String> failures = result.failures();
 

exceptionsVia

@RequiresNonNull(value="fn")
public <FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K1,V>,KV<K2,V>,FailureT> exceptionsVia(InferableFunction<WithFailures.ExceptionElement<KV<K1,V>>,FailureT> exceptionHandler)

Returns a new SimpleMapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.

This method takes advantage of the type information provided by InferableFunction, meaning that a call to exceptionsInto(TypeDescriptor) may not be necessary.

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

Example usage:

{@code
 Result>, String> result =
         input.apply(
             MapKeys.into(TypeDescriptors.integers())
                 .via(word -> 1 / word.length)  // Could throw ArithmeticException
                 .exceptionsVia(
                     new InferableFunction>, String>() {

expand

public PCollection<KV<K2,V>> expand(PCollection<KV<K1,V>> 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<KV<K1,V>>,PCollection<KV<K2,V>>>