com.google.appengine.tools.mapreduce.outputs

Class LevelDbOutput<R>

java.lang.Object

com.google.appengine.tools.mapreduce.Output<ByteBuffer,R>

com.google.appengine.tools.mapreduce.outputs.LevelDbOutput<R>

Type Parameters:

R - type returned by finish(java.util.Collection<? extends com.google.appengine.tools.mapreduce.OutputWriter<java.nio.ByteBuffer>>)

All Implemented Interfaces:

Serializable

public class LevelDbOutput<R>
extends Output<ByteBuffer,R>

An Output that writes LevelDb records. Data written with this class can be read with GoogleCloudStorageLevelDbInput.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LevelDbOutput(Output<ByteBuffer,R> sink)

Method Summary

Methods

Modifier and Type	Method and Description
List<LevelDbOutputWriter>	createWriters(int numShards) Returns a list of writers, one for each shard, for this output.
R	finish(Collection<? extends OutputWriter<ByteBuffer>> writers) Returns a result to be made available through MapReduceResult.getOutputResult().

Methods inherited from class com.google.appengine.tools.mapreduce.Output

getContext, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

LevelDbOutput

public LevelDbOutput(Output<ByteBuffer,R> sink)

Parameters:

sink - The output where data should be written.

Method Detail

createWriters

public List<LevelDbOutputWriter> createWriters(int numShards)

Description copied from class: Output

Returns a list of writers, one for each shard, for this output.

Specified by:

createWriters in class Output<ByteBuffer,R>

Parameters:

numShards - The number of shards which should be equal to the number of OutputWriters returned.

finish

public R finish(Collection<? extends OutputWriter<ByteBuffer>> writers)
         throws IOException

Description copied from class: Output

Returns a result to be made available through MapReduceResult.getOutputResult().

This method allows the Output to inspect the final state of its OutputWriters to produce a final result object. For example, if the OutputWriters produce blobs in blobstore, finish could collect and return a list of blob IDs.

Should return null if no such result makes sense for this kind of output.

Called after all OutputWriters have been closed (with OutputWriter.close()). It is possible for this method to be called more than once with the same writers collection. It is also possible for the job to fail after this is invoked.

The writers argument will contain the same writers that Output.createWriters(int) returned in the same order. Writers may be serialized and deserialized multiple times. typically, getWriter will have been called in a different JVM.

Specified by:

finish in class Output<ByteBuffer,R>

Throws:

IOException