HLL_COUNT_MERGE_PARTIAL

Takes one or more HLL++ sketch inputs and merges them into a new sketch.

Each sketch must be built on the same type and the same precision. Attempts to merge sketches for different types or precision results in an error. For example, you cannot merge a sketch built from INTEGER data with one built from TEXT data, or a sketch built with 13 precision and a sketch built with 14 precision.

If the input expression is NULL or empty, this function returns NULL.

Syntax

HLL_COUNT_MERGE_PARTIAL ( <expression> )

Parameters

Return Type

BYTEA

Example

SELECT
    HLL_COUNT_MERGE_PARTIAL(hll_sketch) as merged_sketches
FROM
    sketch_table;

Returns:

A merged HLL++ sketch represented in data type BYTEA.