| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | "Bossart, Nathan" <bossartn(at)amazon(dot)com> |
| Cc: | Magnus Hagander <magnus(at)hagander(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Vik Fearing <vik(at)postgresfriends(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Catalog version access |
| Date: | 2022-01-24 03:30:49 |
| Message-ID: | Ye4daRe1ytSBE64/@paquier.xyz |
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| Lists: | pgsql-hackers |
On Mon, Aug 16, 2021 at 06:12:54PM +0000, Bossart, Nathan wrote:
> I was looking at the --check switch for the postgres binary recently
> [0], and this sounds like something that might fit in nicely there.
> In the attached patch, --check will also check the control file if one
> exists.
This would not work on a running postmaster as CreateDataDirLockFile()
is called beforehand, but we want this capability, no?
Abusing a bootstrap option for this purpose does not look like a good
idea, to be honest, especially for something only used internally now
and undocumented, but we want to use something aimed at an external
use with some documentation. Using a separate switch would be more
adapted IMO. Also, I think that we should be careful with the read of
the control file to avoid false positives? We can rely on an atomic
read/write thanks to its maximum size of 512 bytes, but this looks
like a lot what has been done recently with postgres -C for runtime
GUCs, that *require* a read of the control file before grabbing the
values we are interested in.
--
Michael
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