Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Simon Riggs <simon.riggs@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Jakub Wartak <jakub.wartak@enterprisedb.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2022-11-22T16:35:00Z
Lists: pgsql-hackers 
Simon Riggs <simon.riggs@enterprisedb.com> writes:
> New patch version reporting for duty, sir. Please take it from here!

Why the CHECK_FOR_INTERRUPTS?  I'd supposed that there's going to be
one somewhere down inside the index or heap access --- do you have
reason to think there isn't?

Is it appropriate to count distinct pages, rather than just the
number of times we have to visit a heap tuple?  That seems to
complicate the logic a good deal, and I'm not sure it's buying
much, especially since (as you noted) it's imprecise anyway.

			regards, tom lane

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.