Hi,
On 2022-04-14 15:05:50 -0400, Tom Lane wrote:
> Andres' complaint is that that snapshot might get invalidated when you
> weren't expecting it, but I'm not really convinced that we have all
> that many bugs of that ilk. Wouldn't CLOBBER_CACHE_ALWAYS testing
> find them?
Don't see why it would - we don't have any mechanism in place for
enforcing that we don't update / delete a tuple we've looked up with an
xmin that wasn't continually enforced. A typical pattern is to use a
catalog cache (registered an all) for a syscache lookup, but then not
have a registered / active snapshot until an eventual update / delete
(after the syscache scan ends). Which isn't safe, because without a
MyProc->xmin set, the tuple we're updating / deleting could be updated,
removed and replaced with another tuple.
Greetings,
Andres Freund
