ClickHouse/00453_top_k.sql at 868c1bd70b72021632d30a9f73255ef5ae216b41 - ClickHouse - gitea@var1able.network

thevar1able/ClickHouse

mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-11-16 20:53:27 +00:00

Marek Vavruša 5f1e65b252 AggregateFunctions: implemented topK(n)

This implements a new function for approximate
computation of the most frequent entries using
Filtered Space Saving with a merge step adapted
from Parallel Space Saving paper.

It works better for cases where GROUP BY x
is impractical due to high cardinality of x,
such as top IP addresses or top search queries.

2017-05-03 23:09:52 -07:00

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SQL

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SELECT topK(10)(n) FROM (SELECT if(number % 100 < 10, number % 10, number) AS n FROM system.numbers LIMIT 100000);