Re: found xmin from before relfrozenxid on pg_catalog.pg_authid

On 2018-05-26 13:45:06 -0700, Andres Freund wrote:
> On 2018-05-25 15:05:31 -0700, Andres Freund wrote:
> > On 2018-05-25 17:47:37 -0400, Tom Lane wrote:
> > > For nailed indexes, we allow updating of some additional fields, and I
> > > guess what has to happen here is that we teach the code to update some
> > > additional fields for nailed tables too.
> >
> > Yea, it seems like we could just get a new version of the pg_class tuple
> > if in the right state, and memcpy() it into place. Not sure if there's
> > any other issues...
>
> That part isn't too hard. I've a patch that appears to address the
> issue, and isn't *too* ugly.
>
> We don't really have a way to force .init file removal / update for
> shared relations however. Otherwise we'll just continue to read old data
> from .init files at startup. And there'll commonly not be any
> outstanding invalidation. Thus it appears to me that we need to extend
> RelcacheInitFileInval to also support the shared file. That's WAL
> logged, but it looks like we can just add flag like
> XACT_COMPLETION_UPDATE_RELCACHE_FILE without breaking the WAL format.
>
> Does anybody see a way to not have to remove the .init file?

Just to be clear: We already remove the non-shared relcache init file
when a non-shared table in it is changed . Which I presume is the reason
this issue hasn't bitten us in a much bigger way. While the lack of
proper invalidations means that already running sessions will see the
wrong values and make wrong decisions, the fact that the non-shared file
will regularly be removed has reduced the impact quite a bit.

Greetings,

Andres Freund