Re: Why is get_actual_variable_range()'s use of SnapshotNonVacuumable safe during recovery?

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Why is get_actual_variable_range()'s use of SnapshotNonVacuumable safe during recovery?
Date: 2019-12-14 00:48:39
Message-ID: CAH2-Wz=di9cyiqdby36YDKi4M33_U3KG-gzE3U7Uo-Mtm+h82Q@mail.gmail.com
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On Wed, Nov 20, 2019 at 1:43 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> My understanding is that we can trust RecentGlobalXmin to be something
> useful and current during recovery, in general, so the selfuncs.c
> index-only scan (which uses SnapshotNonVacuumable + RecentGlobalXmin)
> can be trusted to work just as well as it would on the primary. Does
> that sound correct?

Nobody wants to chime in on this?

I would like to fix the nbtree README soon. It's kind of standing in
the way of my plan to finish off the work started by Simon's commit
3e4b7d87, and remove the remaining remnants of nbtree VACUUM "pin
scans". Apart from anything else, the current organisation of the code
is contradictory.

--
Peter Geoghegan

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