Package dev.frostlake.functions.aggregate

Class ApproxTopKAccumulator

java.lang.Object

dev.frostlake.functions.aggregate.ApproxTopKAccumulator

All Implemented Interfaces:

ConstantArgumentsAccumulator, AggregateFunction.Accumulator, MultiArgumentAccumulator

public class ApproxTopKAccumulator
extends Object
implements AggregateFunction.Accumulator, MultiArgumentAccumulator, ConstantArgumentsAccumulator

The accumulator of ApproxTopK: a TopKSummary sized by the call's third argument, answering the first k of its ranking. The limits come from the argument texts (so an empty group is still sized as written) and, when no texts were given, from the first row's constant values.

Constructor Summary

Constructors

Constructor	Description
ApproxTopKAccumulator()

Method Summary

Modifier and Type	Method	Description
void	accumulate(Object value)	Folds one row's argument value into the running state.
void	accumulate(List<Object> argumentValues)	One row's values, one per declared argument, in the order the call wrote them.
Object	getResult()	The aggregate's result over everything accumulated so far.
void	merge(AggregateFunction.Accumulator other)	Folds another accumulator's state into this one, combining two partial aggregations of the same group.
void	reset()	Clears the state back to the empty-group starting point so the accumulator can be reused.
void	setConstantArgumentTexts(List<String> argumentTexts)

Methods inherited from class java.lang.Object

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

Constructor Details

ApproxTopKAccumulator

public ApproxTopKAccumulator()

Method Details

setConstantArgumentTexts

public void setConstantArgumentTexts(List<String> argumentTexts)

Specified by:

setConstantArgumentTexts in interface ConstantArgumentsAccumulator

accumulate

public void accumulate(List<Object> argumentValues)

Description copied from interface: MultiArgumentAccumulator

One row's values, one per declared argument, in the order the call wrote them.

Specified by:

accumulate in interface MultiArgumentAccumulator

accumulate

public void accumulate(Object value)

Description copied from interface: AggregateFunction.Accumulator

Folds one row's argument value into the running state.

Specified by:

accumulate in interface AggregateFunction.Accumulator

Parameters:

value - the aggregate argument's value for one row; SQL NULL arrives as null

getResult

public Object getResult()

Description copied from interface: AggregateFunction.Accumulator

The aggregate's result over everything accumulated so far.

Specified by:

getResult in interface AggregateFunction.Accumulator

Returns:

the group's result, or null where the aggregate defines an empty group as NULL

reset

public void reset()

Description copied from interface: AggregateFunction.Accumulator

Clears the state back to the empty-group starting point so the accumulator can be reused.

Specified by:

reset in interface AggregateFunction.Accumulator

merge

public void merge(AggregateFunction.Accumulator other)

Description copied from interface: AggregateFunction.Accumulator

Folds another accumulator's state into this one, combining two partial aggregations of the same group.

Specified by:

merge in interface AggregateFunction.Accumulator

Parameters:

other - a partial state of the same aggregate implementation