thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-11-29 19:12:03 +00:00
Code Issues Packages Projects Releases Wiki Activity
fd14d168df
ClickHouse/docs/en/sql-reference/aggregate-functions/reference/uniqthetasketch.md
rfraposa 869967de41 Remove H1 anchor tags from docs
2022-06-02 04:55:18 -06:00

1.5 KiB
Raw Blame History

sidebar_position
195

uniqTheta

Calculates the approximate number of different argument values, using the Theta Sketch Framework.

uniqTheta(x[, ...])

Arguments

The function takes a variable number of parameters. Parameters can be Tuple, Array, Date, DateTime, String, or numeric types.

Returned value

Implementation details

Function:

  • Calculates a hash for all parameters in the aggregate, then uses it in calculations.

  • Uses the KMV algorithm to approximate the number of different argument values.

    4096(2^12) 64-bit sketch are used. The size of the state is about 41 KB.

  • The relative error is 3.125% (95% confidence), see the relative error table for detail.

See Also