Package org.apache.druid.query.topn

Class Generic1AggPooledTopNScannerPrototype

java.lang.Object

org.apache.druid.query.topn.Generic1AggPooledTopNScannerPrototype

All Implemented Interfaces:

Generic1AggPooledTopNScanner

public final class Generic1AggPooledTopNScannerPrototype
extends Object
implements Generic1AggPooledTopNScanner

Constructor Summary

Constructors

Constructor	Description
Generic1AggPooledTopNScannerPrototype()

Method Summary

Modifier and Type	Method	Description
long	scanAndAggregate(DimensionSelector dimensionSelector, BufferAggregator aggregator, int aggregatorSize, Cursor cursor, int[] positions, ByteBuffer resultsBuffer)	Any changes to this method should be coordinated with TopNUtils, PooledTopNAlgorithm.computeSpecializedScanAndAggregateImplementations() and downstream methods.

Methods inherited from class java.lang.Object

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

Constructor Detail

Generic1AggPooledTopNScannerPrototype

public Generic1AggPooledTopNScannerPrototype()

Method Detail

scanAndAggregate

public long scanAndAggregate(DimensionSelector dimensionSelector,
                             BufferAggregator aggregator,
                             int aggregatorSize,
                             Cursor cursor,
                             int[] positions,
                             ByteBuffer resultsBuffer)

Any changes to this method should be coordinated with TopNUtils, PooledTopNAlgorithm.computeSpecializedScanAndAggregateImplementations() and downstream methods. It should be checked with a tool like https://github.com/AdoptOpenJDK/jitwatch that C2 compiler output for this method doesn't have any method calls in the while loop, i. e. all method calls are inlined. To be able to see assembly of this method in JITWatch and other similar tools, PooledTopNAlgorithm.SPECIALIZE_GENERIC_ONE_AGG_POOLED_TOPN should be turned off. Note that in this case the benchmark should be "naturally monomorphic", i. e. execute this method always with the same runtime shape. If the while loop contains not inlined method calls, it should be considered as a performance bug.

Specified by:

scanAndAggregate in interface Generic1AggPooledTopNScanner

aggregatorSize - number of bytes required by aggregator for a single aggregation

positions - a cache for positions in resultsBuffer, where specific (indexed) dimension values are aggregated

Returns:

number of scanned rows, i. e. number of steps made with the given cursor