Horton

Re: Damage control for planner's get_actual_variable_endpoint() runaway

Simon Riggs <simon.riggs@enterprisedb.com>

View thread View on postgr.es
From: Simon Riggs <simon.riggs@enterprisedb.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Jakub Wartak <jakub.wartak@enterprisedb.com>, Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2022-11-22T16:17:34Z
Lists: pgsql-hackers

Attachments

On Mon, 21 Nov 2022 at 20:55, Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Mon, Nov 21, 2022 at 1:17 PM Andres Freund <andres@anarazel.de> wrote:
> > On November 21, 2022 9:37:34 AM PST, Robert Haas <robertmhaas@gmail.com> wrote:
> > >On Mon, Nov 21, 2022 at 12:30 PM Andres Freund <andres@anarazel.de> wrote:
> > >> This can't quite be right - isn't this only applying the limit if we found a
> > >> visible tuple?
> > >
> > >It doesn't look that way to me, but perhaps I'm just too dense to see
> > >the problem?
> >
> > The earlier version didn't have the issue, but the latest seems to only limit after a visible tuple has been found. Note the continue; when fetching a heap tuple fails.
>
> Oh, that line was removed in Simon's patch but not in Jakub's version,
> I guess. Jakub's version also leaves out the last_block = block line
> which seems pretty critical.

New patch version reporting for duty, sir. Please take it from here!

-- 
Simon Riggs                http://www.EnterpriseDB.com/

Commits

  1. YA attempt at taming worst-case behavior of get_actual_variable_range.

  2. Improve performance of get_actual_variable_range with recently-dead tuples.

  3. Use SnapshotDirty rather than an active snapshot to probe index endpoints.