groupBitmap | RawTree

Creates a bitmap (bit array) from a column of unsigned integers, then returns the count of unique values (cardinality) in that bitmap.

Creates a bitmap (bit array) from a column of unsigned integers, then returns the count of unique values (cardinality) in that bitmap. By appending the -State combinator suffix, instead of returning the count, it returns the actual bitmap object.

Syntax

groupBitmap(expr)
groupBitmapState(expr)

Arguments

expr — Expression that results in a UInt* type. UInt*

Returned value

Returns the count of type UInt64 type, or a bitmap object when using -State. UInt64

Examples

Usage example

CREATE TABLE t (UserID UInt32) ENGINE = Memory;
INSERT INTO t VALUES (1), (1), (2), (3);

SELECT groupBitmap(UserID) AS num FROM t;

┌─num─┐
│   3 │
└─────┘

Introduced in version 20.1.