io.prestosql.operator.project

Class MergingPageOutput

java.lang.Object

io.prestosql.operator.project.MergingPageOutput

@NotThreadSafe
public class MergingPageOutput
extends Object

This class is intended to be used right after the PageProcessor to ensure that the size of the pages returned by FilterAndProject and ScanFilterAndProject is big enough so it does not introduce considerable synchronization overhead.

As long as the input page contains more than minRowCount rows or is bigger than minPageSizeInBytes it is returned as is without additional memory copy.

The page data that has been buffered so far before receiving a "big" page is being flushed before transferring a "big" page.

Although it is still possible that the MergingPageOutput may return a tiny page, this situation is considered to be rare due to the assumption that filter selectivity may not vary a lot based on the particular input page.

Considering the CPU time required to process(filter, project) a full (~1MB) page returned by a connector, the CPU cost of memory copying (< 50kb, < 1024 rows) is supposed to be negligible.

Constructor Summary

Constructors

Constructor and Description
MergingPageOutput(Iterable<? extends Type> types, long minPageSizeInBytes, int minRowCount)
MergingPageOutput(Iterable<? extends Type> types, long minPageSizeInBytes, int minRowCount, int maxPageSizeInBytes)

Method Summary

Modifier and Type	Method and Description
void	addInput(Iterator<Optional<Page>> input)
void	finish()
Page	getOutput()
long	getRetainedSizeInBytes()
boolean	isFinished()
boolean	needsInput()

Methods inherited from class java.lang.Object

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

Constructor Detail

MergingPageOutput

public MergingPageOutput(Iterable<? extends Type> types,
                         long minPageSizeInBytes,
                         int minRowCount)

MergingPageOutput

public MergingPageOutput(Iterable<? extends Type> types,
                         long minPageSizeInBytes,
                         int minRowCount,
                         int maxPageSizeInBytes)

Method Detail

needsInput

public boolean needsInput()

addInput

public void addInput(Iterator<Optional<Page>> input)

getOutput

@Nullable
public Page getOutput()

finish

public void finish()

isFinished

public boolean isFinished()

getRetainedSizeInBytes

public long getRetainedSizeInBytes()