Horton

Re: Race condition in TransactionIdIsInProgress

Simon Riggs <simon.riggs@enterprisedb.com>

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From: Simon Riggs <simon.riggs@enterprisedb.com>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Konstantin Knizhnik <knizhnik@garret.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2022-02-11T08:48:43Z
Lists: pgsql-hackers 
On Fri, 11 Feb 2022 at 06:11, Andres Freund <andres@anarazel.de> wrote:

> Looks lik syncrep will make this a lot worse, because it can drastically
> increase the window between the TransactionIdCommitTree() and
> ProcArrayEndTransaction() due to the SyncRepWaitForLSN() inbetween.  But at
> least it might make it easier to write tests exercising this scenario...

Agreed

TransactionIdIsKnownCompleted(xid) is only broken because the single
item cache is set too early in some cases. The single item cache is
important for performance, so we just need to be more careful about
setting the cache.

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

Commits

  1. Fix visibility check when XID is committed in CLOG but not in procarray.

  2. Fix possible HOT corruption when RECENTLY_DEAD changes to DEAD while pruning.

  3. Make TransactionIdIsInProgress check transam.c's single-item XID status cache