Package org.apache.druid.frame.channel

Class ReadableConcatFrameChannel

java.lang.Object

org.apache.druid.frame.channel.ReadableConcatFrameChannel

All Implemented Interfaces:

Closeable, AutoCloseable, ReadableFrameChannel

public class ReadableConcatFrameChannel
extends Object
implements ReadableFrameChannel

Channel that concatenates a sequence of other channels that are provided by an iterator. The iterator is walked just-in-time, meaning that Iterator.next() is not called until the channel is actually ready to be used. The first channel is pulled from the iterator immediately upon construction.

Method Summary

Modifier and Type	Method	Description
boolean	canRead()	Returns whether this channel has a batch of data or error condition currently available.
void	close()	Releases any resources associated with this readable channel.
boolean	isFinished()	Returns whether this channel is finished.
static ReadableConcatFrameChannel	open(Iterator<ReadableFrameChannel> channelIterator)	Creates a new concatenated channel.
RowsAndColumns	read()	Returns the next available batch of data from this channel as a RowsAndColumns.
com.google.common.util.concurrent.ListenableFuture<?>	readabilityFuture()	Returns a future that will resolve when either ReadableFrameChannel.isFinished() or ReadableFrameChannel.canRead() would return true.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.druid.frame.channel.ReadableFrameChannel

readFrame

Method Details

open

public static ReadableConcatFrameChannel open(Iterator<ReadableFrameChannel> channelIterator)

Creates a new concatenated channel. The first channel is pulled from the provided iterator immediately. Other channels are pulled on-demand, when they are ready to be used.

isFinished

public boolean isFinished()

Description copied from interface: ReadableFrameChannel

Returns whether this channel is finished. Finished channels will not generate any further data batches or errors. Generally, once you discover that a channel is finished, you should call ReadableFrameChannel.close() and then discard it. Note that it is possible for a channel to be unfinished and also have no available data batches or errors. This happens when it is not in a ready-for-reading state. See ReadableFrameChannel.readabilityFuture() for details.

Specified by:

isFinished in interface ReadableFrameChannel

canRead

public boolean canRead()

Description copied from interface: ReadableFrameChannel

Returns whether this channel has a batch of data or error condition currently available. If this method returns true, then you can call ReadableFrameChannel.readFrame() or ReadableFrameChannel.read() to retrieve the batch or error. Note that it is possible for a channel to be unfinished and also have no available batches or errors. This happens when it is not in a ready-for-reading state. See ReadableFrameChannel.readabilityFuture() for details.

Specified by:

canRead in interface ReadableFrameChannel

read

public RowsAndColumns read()

Description copied from interface: ReadableFrameChannel

Returns the next available batch of data from this channel as a RowsAndColumns. Before calling this method, you should check ReadableFrameChannel.canRead() to ensure there is a batch of data or error available.

Specified by:

read in interface ReadableFrameChannel

readabilityFuture

public com.google.common.util.concurrent.ListenableFuture<?> readabilityFuture()

Description copied from interface: ReadableFrameChannel

Returns a future that will resolve when either ReadableFrameChannel.isFinished() or ReadableFrameChannel.canRead() would return true. The future will never resolve to an exception. If something exceptional has happened, the exception can be retrieved from ReadableFrameChannel.readFrame() or ReadableFrameChannel.read().

Specified by:

readabilityFuture in interface ReadableFrameChannel

close

public void close()

Description copied from interface: ReadableFrameChannel

Releases any resources associated with this readable channel. After calling this, you should not call any other methods on the channel.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface ReadableFrameChannel