topk_agg

Description

Returns an approximation of the top K most frequent values in the input, along with their approximate frequencies.

The output is an array of arrays. In the inner arrays, the first entry is the value in the input, while the second entry is its frequency. The outer array contains k elements, sorted by their frequencies in descending order.

Return type

array of generic array

Domain

This is an aggregate function (aggregates rows over a group in aggregate verbs.)

This is a window function (calculates over a group of multiple input rows using windowing.)

Categories

Usage

topk_agg(expr, k)

Argument

Type

Optional

Repeatable

Restrictions

expr

storable

no

no

none

k

int64

no

no

constant

Examples

statsby top_names:topk_agg(name, 2), group_by(class)

Given the following input:

name

class

Jack

A

Joe

A

Alice

A

Alice

A

Tom

B

Joe

B

Kathy

B

Mike

A

Tom

B

It shall return the following output:

class

top_names

A

[[“Alice”, 2], [“Jack”, 1]]

B

[[“Tom”, 2], [“Kathy”, 1]]

Note that if there is a tie in the last position the result can be non-deterministic. Any of the values with the same frequency may be included in the last position.