Horton

Re: estimation problems for DISTINCT ON with FDW

Jeff Janes <jeff.janes@gmail.com>

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From: Jeff Janes <jeff.janes@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Etsuro Fujita <etsuro.fujita@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-07-25T17:30:22Z
Lists: pgsql-hackers 
On Fri, Jul 3, 2020 at 5:50 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

>
> OK, I'll go ahead and push the patch I proposed yesterday.
>

Thank you.  I tested 12_STABLE with my real queries on the real data set,
and the "hard coded" estimate of 200 distinct rows (when use_remote_estimte
is turned back on) is enough to get rid of the worst plans I was seeing in
12.3.

Cheers,

Jeff

Commits

  1. Clamp total-tuples estimates for foreign tables to ensure planner sanity.