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help / color / mirror / Atom feedFrom: Andrei Lepikhov <[email protected]>
To: Felipe López Montes <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Simple query with Planner underestimating rows.
Date: Wed, 29 Jan 2025 15:57:15 +0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <CACJPJu8CT7wDgKXpx9b7HjavywsjqWUt8Zd3f=bFBa_3tYRs1Q@mail.gmail.com>
References: <CACJPJu-0u221Bker1yn=AJ3xJbW0j29mSM=EvkA_SXecv75hqw@mail.gmail.com>
<[email protected]>
<CACJPJu8CT7wDgKXpx9b7HjavywsjqWUt8Zd3f=bFBa_3tYRs1Q@mail.gmail.com>
On 1/29/25 15:32, Felipe López Montes wrote:
> Hi,
>
> Thank you for your reply,
>
> I have already tried creating such statistics on t3.programme_identifier
> and t3.participant_identifier and the plan is the same, however I cannot
> create them for the right part of the join as they are from different
> tables (t1 and t2)
Of course, because for now, a join clause can't be estimated by extended
statistics. It applies only to a scan filter (clause referencing only
one relation).
I have meant that with the development patch [1] applied, you may create
two statistics on t3(participant_identifier,programme_identifier) and
t2(participant_identifier,programme_identifier). These statistics would
then be used to estimate the join clause and may resolve the problem.
[1] using extended statistics to improve join estimates
https://www.postgresql.org/message-id/flat/c8c0ff31-3a8a-7562-bbd3-78b2ec65f16c%40enterprisedb.com
--
regards, Andrei Lepikhov
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