Re: found xmin from before relfrozenxid on pg_catalog.pg_authid

Hi,

On 2018-05-27 13:00:06 -0700, Andres Freund wrote:
> I've a patch that seems to work, that mostly needs some comment
> polishing.

Attached is what I currently have. Still needs some more work, but I
think it's more than good enough to review the approach. Basically the
approach consists out of two changes:

1) Send init file removals for shared nailed relations as well.

This fixes that the shared init file contains arbitrarily outdated
information for relfrozenxid etc. Leading to e.g. the pg_authid
errors we've seen in some recent threads. Only applies to
new connections.

2) Reread RelationData->rd_rel for nailed relations when invalidated.

This ensures that already built relcache entries for nailed relations
are updated. Currently they never are. This currently doesn't cause
*that* frequently an issue for !shared entries, because for those the
init file gets zapped regularly, and autovacuum workers usually don't
live that long. But it's still a significant correctness issue for
both shared an non shared relations.

FWIW, I wonder if this isn't critical enough to make us consider having
a point release earlier..

Greetings,

Andres Freund