com.google.appengine.tools.mapreduce.inputs

Class DatastoreInputReader

java.lang.Object

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

com.google.appengine.tools.mapreduce.inputs.DatastoreInputReader

All Implemented Interfaces:

Serializable

public class DatastoreInputReader
extends InputReader<V>

An InputReader for Datastore entities.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
DatastoreInputReader(com.google.appengine.api.datastore.Query query)

Method Summary

Methods

Modifier and Type	Method and Description
void	beginShard() Performs setup at the beginning of the shard.
void	beginSlice() Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.
void	endSlice() Prepares the InputReader for serialization.
long	estimateMemoryRequirement() Returns the estimated memory that will be used by this reader in bytes.
protected long	getAvgElementSize()
Double	getProgress() Returns the relative progress reading this input as a number from 0 to 1.
V	next() Returns the next input value, or throws NoSuchElementException when there is no more input data.
String	toString()

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

close, endShard, getContext, open, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

DatastoreInputReader

public DatastoreInputReader(com.google.appengine.api.datastore.Query query)

Method Detail

getAvgElementSize

protected long getAvgElementSize()

next

public V next()

Description copied from class: InputReader

Returns the next input value, or throws NoSuchElementException when there is no more input data. This is done rather than providing a hasNext() function, to allow the implementation to deal with streams and remain serializable, even if the item being read is not.

Specified by:

next in class InputReader<V>

getProgress

public Double getProgress()

Description copied from class: InputReader

Returns the relative progress reading this input as a number from 0 to 1. Returns null if relative progress cannot be determined.

Overrides:

getProgress in class InputReader<V>

beginShard

public void beginShard()

Description copied from class: InputReader

Performs setup at the beginning of the shard. This method is invoked before the first call to InputReader.beginSlice(). It will not be invoked again unless the shard restarts. When a shard is restarted, this method is invoked and the input should be read from the beginning.

Overrides:

beginShard in class InputReader<V>

endSlice

public void endSlice()

Description copied from class: InputReader

Prepares the InputReader for serialization.

Overrides:

endSlice in class InputReader<V>

beginSlice

public void beginSlice()

Description copied from class: InputReader

Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.

Overrides:

beginSlice in class InputReader<V>

estimateMemoryRequirement

public long estimateMemoryRequirement()

Description copied from class: InputReader

Returns the estimated memory that will be used by this reader in bytes. (This is normally just set to the size of the buffers used by the implementation)

Overrides:

estimateMemoryRequirement in class InputReader<V>

toString

public String toString()

Overrides:

toString in class Object