Package dev.frostlake.functions.aggregate

Class ApproxTopK

java.lang.Object

dev.frostlake.functions.BuiltInFunction

dev.frostlake.functions.AggregateFunction

dev.frostlake.functions.aggregate.ApproxTopK

public class ApproxTopK
extends AggregateFunction

APPROX_TOP_K(expr [, k [, counters]]): the k most frequent values of the input as an ARRAY of [value, count] pairs, count descending, computed by the Space-Saving summary in TopKSummary over counters counters (default 100000; k defaults to 1). NULLs are not counted, an empty input is [], and a value keeps its own type inside the pair — a NUMBER renders as a number, a VARCHAR as a string, a VARIANT as itself. The two limits are constants between 1 and 100000, judged at compile time.

As a window function it belongs to the whole-partition family: the bare, PARTITION BY and unbounded ROWS frames are answered, an ORDER BY's cumulative and sliding frames refused.

Nested Class Summary

Nested classes/interfaces inherited from class dev.frostlake.functions.AggregateFunction

AggregateFunction.Accumulator

Constructor Summary

Constructors

Constructor	Description
ApproxTopK()

Method Summary

Modifier and Type	Method	Description
AggregateFunction.Accumulator	createAccumulator()	Creates the fresh, empty per-group state for one evaluation of this aggregate; the executor makes one per group (or per window partition) and never shares them.
Object	evaluate(List<Object> args)	Computes the function's result over its already-evaluated argument values.
int	getMaxArgCount()	The most arguments a call to this function may pass; Integer.MAX_VALUE marks a variadic function (see BuiltInFunction.isVariadic()).
int	getMinArgCount()	The fewest arguments a call to this function may pass; fewer is an argument-count error.

Methods inherited from class dev.frostlake.functions.BuiltInFunction

approximateRejection, binaryRejection, booleanRejection, evaluate, fileRejection, geoRejection, getName, getReturnType, isVariadic, refusesMissingArgumentsByType, semiStructuredRejection, structuredRejection, temporalRejection, temporalRejection, temporalRejection, textRejection, uuidRejection, vectorRejection

Methods inherited from class java.lang.Object

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

Constructor Details

ApproxTopK

public ApproxTopK()

Method Details

createAccumulator

public AggregateFunction.Accumulator createAccumulator()

Description copied from class: AggregateFunction

Creates the fresh, empty per-group state for one evaluation of this aggregate; the executor makes one per group (or per window partition) and never shares them.

Specified by:

createAccumulator in class AggregateFunction

Returns:

a new accumulator starting from this aggregate's empty-group state

evaluate

public Object evaluate(List<Object> args)

Description copied from class: BuiltInFunction

Computes the function's result over its already-evaluated argument values. A SQL NULL argument arrives as Java null, and returning null makes the SQL result NULL.

Specified by:

evaluate in class BuiltInFunction

Parameters:

args - the argument values, in call order

Returns:

the function's value for these arguments, or null for SQL NULL

getMinArgCount

public int getMinArgCount()

Description copied from class: BuiltInFunction

The fewest arguments a call to this function may pass; fewer is an argument-count error.

Specified by:

getMinArgCount in class BuiltInFunction

Returns:

the minimum accepted argument count

getMaxArgCount

public int getMaxArgCount()

Description copied from class: BuiltInFunction

The most arguments a call to this function may pass; Integer.MAX_VALUE marks a variadic function (see BuiltInFunction.isVariadic()).

Specified by:

getMaxArgCount in class BuiltInFunction

Returns:

the maximum accepted argument count