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
