Horton

Re: recovering from "found xmin ... from before relfrozenxid ..."

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Ashutosh Sharma <ashu.coek88@gmail.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, MBeena Emerson <mbeena.emerson@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>
Date: 2020-08-26T15:49:01Z
Lists: pgsql-hackers 
On Wed, Aug 26, 2020 at 7:36 AM Ashutosh Sharma <ashu.coek88@gmail.com> wrote:
> Removed this note from the documentation and added a note saying: "The
> user needs to ensure that they do not operate pg_force_freeze function
> on a deleted tuple because it may revive the deleted tuple."

I do not agree with that note, either. I believe that trying to tell
people what things specifically they should do or avoid doing with the
tool is the wrong approach. Instead, the thrust of the message should
be to tell people that if you use this, it may corrupt your database,
and that's your problem. The difficulty with telling people what
specifically they ought to avoid doing is that experts will be annoyed
to be told that something is not safe when they know that it is fine,
and non-experts will think that some uses are safer than they really
are.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Fix wrong data table horizon computation during backend startup.

  2. Centralize horizon determination for temp tables, fixing bug due to skew.

  3. pg_surgery: Try to stabilize regression tests.

  4. New contrib module, pg_surgery, with heap surgery functions.

  5. Set cutoff xmin more aggressively when vacuuming a temporary table.

  6. snapshot scalability: Don't compute global horizons while building snapshots.

  7. Introduce vacuum errcontext to display additional information.