HLL_UNION_AGG

Description

The HLL_UNION_AGG function is an aggregate function, which is mainly used to merge multiple HyperLogLog data structures and estimate the approximate value of the combined cardinality.

Syntax

hll_union_agg(<hll>)

Parameters

Parameters	Description
<hll>	The HyperLogLog type expression to be calculated

Return Value

Returns the cardinality value of type BIGINT.

Example

select HLL_UNION_AGG(uv_set) from test_uv;

+-------------------------+
| HLL_UNION_AGG(`uv_set`) |
+-------------------------+
| 17721                   |
+-------------------------+