io.crate.data

Class AsyncOperationBatchIterator<T>

java.lang.Object

io.crate.data.AsyncOperationBatchIterator<T>

All Implemented Interfaces:

BatchIterator<T>, Killable

public class AsyncOperationBatchIterator<T>
extends java.lang.Object
implements BatchIterator<T>

BatchIterator implementation which consumes another BatchIterator source. The source data is fed into a BatchAccumulator. Every BatchAccumulator.batchSize() items, BatchAccumulator.processBatch(boolean) is used to create the data for *this* BatchIterator.

 

  (encapsulated via {@link #loadNextBatch()})

   +-> source data
   |      |
   |    batchAccumulator.onItem
   |      |
   |    batchSize reached?
   |          |
   +----------+---+
                  |
                batchAccumulator.processBatch
                      onResult -> fill-up data of *this* BatchIterator
 
 

Constructor Summary

Constructors

Constructor and Description
AsyncOperationBatchIterator(BatchIterator<T> source, BatchAccumulator<T,java.util.Iterator<? extends T>> batchAccumulator)

Method Summary

Modifier and Type	Method and Description
boolean	allLoaded()
void	close() Closes the iterator and frees all resources.
T	currentElement() This method returns the item that is at the current position of the BatchIterator.
void	kill(java.lang.Throwable throwable) Interrupt the operation, increasing the likelihood that it will terminate early with an error.
java.util.concurrent.CompletionStage<?>	loadNextBatch() Loads the next batch if there is still data available for loading.
boolean	moveNext() Advances the iterator.
void	moveToStart() Moves the Iterator back to the starting position.

Methods inherited from class java.lang.Object

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

Constructor Detail

AsyncOperationBatchIterator

public AsyncOperationBatchIterator(BatchIterator<T> source,
                                   BatchAccumulator<T,java.util.Iterator<? extends T>> batchAccumulator)

Method Detail

currentElement

public T currentElement()

Description copied from interface: BatchIterator

This method returns the item that is at the current position of the BatchIterator. The behaviour of this method if the BatchIterator is "not on a position" is undefined.

Specified by:

currentElement in interface BatchIterator<T>

moveToStart

public void moveToStart()

Description copied from interface: BatchIterator

Moves the Iterator back to the starting position. A consumer can then iterate over the rows again by calling into BatchIterator.moveNext() and BatchIterator.loadNextBatch() as appropriate.

Specified by:

moveToStart in interface BatchIterator<T>

moveNext

public boolean moveNext()

Description copied from interface: BatchIterator

Advances the iterator.

Specified by:

moveNext in interface BatchIterator<T>

Returns:

true if the iterator moved to the next valid row. false if the iterator is no longer on a valid row. If BatchIterator.allLoaded() returns true the iterator is out of data. Otherwise BatchIterator.loadNextBatch() can be used to load the next batch - after which moveNext() can be used again.

close

public void close()

Description copied from interface: BatchIterator

Closes the iterator and frees all resources. After this method has been called all methods on the iterator will result in an error. There are two exceptions to that: - close: Close itself can be called multiple times, but only the first call has an effect. - loadNextBatch: This method never raises, but instead returns a failed CompletionStage.

Specified by:

close in interface BatchIterator<T>

loadNextBatch

public java.util.concurrent.CompletionStage<?> loadNextBatch()

Description copied from interface: BatchIterator

Loads the next batch if there is still data available for loading. This may only be called if BatchIterator.allLoaded() returns false. If BatchIterator.allLoaded() returns true, calling this method will return a failed CompletionStage.

NOTE: while loading takes place the iterator must not be moved. The iterator behaviour in this case is undetermined.

Specified by:

loadNextBatch in interface BatchIterator<T>

Returns:

a future which will be completed once the loading is done. Once the future completes the iterator is still in an "off-row" state, but BatchIterator.moveNext() can be called again if the next batch contains more data.

allLoaded

public boolean allLoaded()

Specified by:

allLoaded in interface BatchIterator<T>

Returns:

true if no more batches can be loaded

kill

public void kill(@Nonnull
                 java.lang.Throwable throwable)

Description copied from interface: Killable

Interrupt the operation, increasing the likelihood that it will terminate early with an error. This method can be called concurrently from a different thread while an operation is running.

Implementations must:

• terminate if they're otherwise waiting for input/data
• terminate expensive and long running operations within a reasonable amount of time (< 2sec)

Fast operations which are already running and can complete without further input may ignore the kill. Operations which have already completed may also ignore the kill.

Specified by:

kill in interface Killable

Parameters:

throwable - the reason for the interruption or null if there is none.