Re: Feature request for count_estimate(samplesize) aggregate or SAMPLE keyword - Mailing list pgsql-general

Torge <torgato@posteo.de> writes:
> Now I would like to humbly propose a feature that gives an easy way to 
> get a quick count estimate for any condition - index based or not - 
> based on a random sample of rows, that does not require a custom 
> function creation or complex SQL statement

Can't you do that already using TABLESAMPLE?  For example, to
use a 1% sample:

select count(*) * 100 from mytab tablesample system(1) where <condition>;

You do have to remember to multiply by the factor corresponding
to your sample rate, but aside from that annoyance this (a)
already exists, (b) is SQL-standard, and (c) can be adapted to
a lot of other kinds of analysis besides plain count(*).

            regards, tom lane