Re: CREATE STATISTICS and join selectivity

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: Justin Pryzby <pryzby(at)telsasoft(dot)com>
Cc: postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: CREATE STATISTICS and join selectivity
Date: 2017-11-15 23:47:29
Message-ID: CAKJS1f-6B7KnDFrh6SFhYn-YbHYOXmDDAfd0XC=jJKZMCrfQyg@mail.gmail.com
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On 16 November 2017 at 09:19, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> I just noticed that PG10 CREATE STATISTICS (dependencies) doesn't seem to work
> for joins on multiple columns; is that right?

Unfortunately, for now, they're not used for join selectivity
estimates, only for the base rel selectivities. That's all there was
time for with PG10. This is highly likely to be improved sometime in
the future.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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