public inbox for [email protected]  

help / color / mirror / Atom feed

From: Andres Freund <[email protected]>
To: Peter Geoghegan <[email protected]>
Cc: Justin Pryzby <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations
Date: Thu, 31 Mar 2022 09:37:15 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAH2-WzmwM81qMxjYdm4-Z51PKwsgXXAr21bfBRncXCR7VB8W1g@mail.gmail.com>
	<CAH2-Wzn_LLtTk-jGranhLcciSt_70pFKJNngZOf8Gt_MNgTmnA@mail.gmail.com>
	<[email protected]>
	<CAH2-WzmRZEzeGvLv8yDW0AbFmSvJjTziORqjVUrf74mL4GL0Ww@mail.gmail.com>
	<[email protected]>
	<CAH2-WzkvYTo4rbUi_izHOvcHNw78Ur9xLPGvj1PmDgt-csc8QQ@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<CAH2-WzmN4qh04TcyNph8=1awdUN-nzza_6y+TRbEo-ECiCDV0w@mail.gmail.com>
	<[email protected]>

Hi,

On 2022-03-30 21:59:15 -0700, Andres Freund wrote:
> On 2022-03-30 21:29:16 -0700, Peter Geoghegan wrote:
> > On Wed, Mar 30, 2022 at 9:20 PM Andres Freund <[email protected]> wrote:
> > > Perhaps we should just fetch the horizons from the "local" catalog for shared
> > > rels?
> > 
> > Not sure what you mean.
> 
> Basically, instead of relying on the relcache, which for shared relation is
> vulnerable to seeing "too new" horizons due to the shared relcache init file,
> explicitly load relfrozenxid / relminmxid from the the catalog / syscache.
> 
> I.e. fetch the relevant pg_class row in heap_vacuum_rel() (using
> SearchSysCache[Copy1](RELID)). And use that to set vacrel->relfrozenxid
> etc. Whereas right now we only fetch the pg_class row in
> vac_update_relstats(), but use the relcache before.

Perhaps we should explicitly mask out parts of relcache entries in the shared
init file that we know to be unreliable. I.e. set relfrozenxid, relminmxid to
Invalid* or such.

I even wonder if we should just generally move those out of the fields we have
in the relcache, not just for shared rels loaded from the init
fork. Presumably by just moving them into the CATALOG_VARLEN ifdef.

The only place that appears to access rd_rel->relfrozenxid outside of DDL is
heap_abort_speculative().

Greetings,

Andres Freund

view thread (72+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox