com.google.appengine.tools.mapreduce.inputs

Class DatastoreInput

java.lang.Object

com.google.appengine.tools.mapreduce.Input<V>

com.google.appengine.tools.mapreduce.inputs.DatastoreInput

All Implemented Interfaces:

Serializable

public final class DatastoreInput
extends Input<V>

An input to read entities of a specified kind from the datastore.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
DatastoreInput(com.google.appengine.api.datastore.Query query, int shardCount)
DatastoreInput(String entityKind, int shardCount)
DatastoreInput(String entityKind, int shardCount, String namespace)

Method Summary

Methods

Modifier and Type	Method and Description
protected DatastoreInputReader	createReader(com.google.appengine.api.datastore.Query query)
List<InputReader<V>>	createReaders() Returns a list of readers for this input.
int	getShardCount()

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

getContext

Methods inherited from class java.lang.Object

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

Constructor Detail

DatastoreInput

public DatastoreInput(String entityKind,
              int shardCount)

Parameters:

entityKind - entity kind to read from the datastore.

shardCount - number of parallel shards for the input.

DatastoreInput

public DatastoreInput(String entityKind,
              int shardCount,
              String namespace)

Parameters:

entityKind - entity kind to read from the datastore.

shardCount - number of parallel shards for the input.

namespace - the namespace of the entities (if null will use current).

DatastoreInput

public DatastoreInput(com.google.appengine.api.datastore.Query query,
              int shardCount)

Parameters:

query - the query to read from the datastore.

shardCount - the number for parallel shards for the input.

Method Detail

createReader

protected DatastoreInputReader createReader(com.google.appengine.api.datastore.Query query)

createReaders

public List<InputReader<V>> createReaders()

Description copied from class: Input

Returns a list of readers for this input. It is the Input's responsibility to determine an appropriate number of readers to split into. This could be specified by the user or determined algorithmically. The number of input readers returned determines the number of map shards.

Specified by:

createReaders in class Input<V>

getShardCount

public int getShardCount()