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HLL_COUNT_EXTRACT

Extracts a cardinality estimate of a single HLL++ sketch.

If the sketch is NULL, this function returns a cardinality estimate of 0.

Syntax 

HLL_COUNT_EXTRACT ( <expression> )

Parameters

Parameter Description Supported input types
<expression> An HLL++ sketch in a valid format, e.g. the output of the HLL_COUNT_BUILD function. BYTEA

Return Type

BIGINT

Example 

SELECT
    HLL_COUNT_EXTRACT(hll_sketches) as count_distinct, hll_sketches
FROM
    sketch_table;

Returns:

The cardinality estimates of HLL++ sketches represented as data type BYTEA.

count_distinct hll_sketches
5 \x2f41676772656761746546756e6374696f6e28312c20756e6971436f6d62696e65643634283132292c20496e743332290a01052ccbc234fcbc56b4e7830665202abf3aced8f809c581510b7518f0a86804904775554cd537d76ad6
6 \x2f41676772656761746546756e6374696f6e28312c20756e6971436f6d62696e65643634283132292c20496e743332290c01062ccbc234fcbc56b4e7830665202abf3aced8f809c581510bddd168e4cb29077487c6a393a5ccab46d5f1f4f71f9a2091