Package org.apache.druid.frame.processor
Class FrameChannelMerger
- java.lang.Object
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- org.apache.druid.frame.processor.FrameChannelMerger
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- All Implemented Interfaces:
FrameProcessor<Long>
public class FrameChannelMerger extends Object implements FrameProcessor<Long>
Processor that merges already-sorted inputChannels and writes a fully-sorted stream to a single outputChannel. Frames from input channels must beFrameType.ROW_BASED
. Output frames will be row-based as well. For unsorted output, useFrameChannelMixer
instead.
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Constructor Summary
Constructors Constructor Description FrameChannelMerger(List<ReadableFrameChannel> inputChannels, FrameReader frameReader, WritableFrameChannel outputChannel, FrameWriterFactory frameWriterFactory, List<KeyColumn> sortKey, ClusterByPartitions partitions, long rowLimit)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
cleanup()
Closes resources used by this worker.List<ReadableFrameChannel>
inputChannels()
List of input channels.List<WritableFrameChannel>
outputChannels()
List of output channels.ReturnOrAwait<Long>
runIncrementally(it.unimi.dsi.fastutil.ints.IntSet readableInputs)
Runs some of the algorithm, without blocking, and either returns a value or a set of input channels to wait for.
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Constructor Detail
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FrameChannelMerger
public FrameChannelMerger(List<ReadableFrameChannel> inputChannels, FrameReader frameReader, WritableFrameChannel outputChannel, FrameWriterFactory frameWriterFactory, List<KeyColumn> sortKey, @Nullable ClusterByPartitions partitions, long rowLimit)
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Method Detail
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inputChannels
public List<ReadableFrameChannel> inputChannels()
Description copied from interface:FrameProcessor
List of input channels. The positions of channels in this list are used to build thereadableInputs
set provided toFrameProcessor.runIncrementally(it.unimi.dsi.fastutil.ints.IntSet)
.- Specified by:
inputChannels
in interfaceFrameProcessor<Long>
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outputChannels
public List<WritableFrameChannel> outputChannels()
Description copied from interface:FrameProcessor
List of output channels.- Specified by:
outputChannels
in interfaceFrameProcessor<Long>
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runIncrementally
public ReturnOrAwait<Long> runIncrementally(it.unimi.dsi.fastutil.ints.IntSet readableInputs) throws IOException
Description copied from interface:FrameProcessor
Runs some of the algorithm, without blocking, and either returns a value or a set of input channels to wait for. This method is called byFrameProcessorExecutor.runFully(org.apache.druid.frame.processor.FrameProcessor<T>, java.lang.String)
when all output channels are writable. Therefore, it is guaranteed that each output channel can accept at least one frame. This method must not read more than one frame from each readable input channel, and must not write more than one frame to each output channel.- Specified by:
runIncrementally
in interfaceFrameProcessor<Long>
- Parameters:
readableInputs
- channels fromFrameProcessor.inputChannels()
that are either finished or ready to read. That is: eitherReadableFrameChannel.isFinished()
orReadableFrameChannel.canRead()
are true.- Returns:
- either a final return value or a set of input channels to wait for. Must be nonnull.
- Throws:
IOException
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cleanup
public void cleanup() throws IOException
Description copied from interface:FrameProcessor
Closes resources used by this worker. Exact same concept asCloseable.close()
. This interface does not extend Closeable, in order to make it easier to find all places where cleanup happens. (Static analysis tools can lose the thread when Closeables are closed in generic ways.) Implementations typically callReadableFrameChannel.close()
andWritableFrameChannel.close()
on all input and output channels, as well as releasing any additional resources that may be held, such asFrameWriter
. In cases of cancellation, this method may be called even ifFrameProcessor.runIncrementally(it.unimi.dsi.fastutil.ints.IntSet)
has not yet returned a result viaReturnOrAwait.returnObject(T)
.- Specified by:
cleanup
in interfaceFrameProcessor<Long>
- Throws:
IOException
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