groupArraySample

Introduced in: v20.3.0 Creates an array of sample argument values. The size of the resulting array is limited to max_size elements. Argument values are selected and added to the array randomly. Syntax

groupArraySample(max_size[, seed])(x)

Parameters

max_size — Maximum size of the resulting array. UInt64
seed — Optional. Seed for the random number generator. When omitted, every aggregation state seeds itself from a thread-local generator, so the sample is different for every evaluation and the function is non-deterministic. Pass a seed for a reproducible sample. UInt64
x — Argument (column name or expression). Any

Arguments

array_column — Column containing arrays to be aggregated. Array

Returned value Array of randomly selected x arguments. Array(T) Examples Usage example

Query

CREATE TABLE colors (
    id Int32,
    color String
) ENGINE = Memory;

INSERT INTO colors VALUES
(1, 'red'),
(2, 'blue'),
(3, 'green'),
(4, 'white'),
(5, 'orange');

SELECT groupArraySample(3)(color) as newcolors FROM colors;

Response

┌─newcolors──────────────────┐
│ ['white','blue','green']   │
└────────────────────────────┘

Example using a seed

Query

-- Query with column name and different seed
SELECT groupArraySample(3, 987654321)(color) as newcolors FROM colors;

Response

┌─newcolors────────────────┐
│ ['red','orange','green'] │
└──────────────────────────┘

Using an expression as an argument

Query

-- Query with expression as argument
SELECT groupArraySample(3)(concat('light-', color)) as newcolors FROM colors;

Response

┌─newcolors───────────────────────────────────┐
│ ['light-blue','light-orange','light-green'] │
└─────────────────────────────────────────────┘

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groupArraySample

groupArraySample

​groupArraySample

groupArraySample