Horton

Re: snapshot too old issues, first around wraparound and then more.

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Peter Geoghegan <pg@bowt.ie>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Kevin Grittner <kgrittn@gmail.com>
Date: 2021-06-15T17:10:36Z
Lists: pgsql-hackers 
Hi,

On 2021-06-15 12:51:28 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > Oh, maybe I'm the one who misunderstood...
> 
> So, it's well over a year later, and so far as I can see exactly
> nothing has been done about snapshot_too_old's problems.
> 
> I never liked that feature to begin with, and I would be very
> glad to undertake the task of ripping it out.  If someone thinks
> this should not happen, please commit to fixing it ... and not
> "eventually".

I still think that's the most reasonable course. I actually like the
feature, but I don't think a better implementation of it would share
much if any of the current infrastructure.

Greetings,

Andres Freund

Commits

  1. Remove the "snapshot too old" feature.

  2. Improve timeout.c's handling of repeated timeout set/cancel.

  3. Fix two bugs in MaintainOldSnapshotTimeMapping.