On Thu, Oct 21, 2021 at 07:21 Stan Hu <sta...@gmail.com> wrote: > On Wed, Oct 20, 2021 at 9:01 PM Kyotaro Horiguchi > <horikyota....@gmail.com> wrote: > > > > lastOverflowedXid is the smallest subxid that possibly exists but > > possiblly not known to the standby. So if all top-level transactions > > older than lastOverflowedXid end, that means that all the > > subtransactions in doubt are known to have been ended. > > Thanks for the patch! I verified that it appears to reset > lastOverflowedXid properly. >
Is it right time to register the patch in the current commit fest, right? (How to do that?) On a separate note, I think it would be really good to improve observability for SLRUs -- particularly for Subtrans SLRU and this overflow-related aspects. pg_stat_slru added in PG13 is really helpful, but not enough to troubleshoot, analyze and tune issues like this, and the patches related to SLRU. Basic ideas: - expose to the user how many pages are currently used (especially useful if SLRU sizes will be configurable, see https://commitfest.postgresql.org/34/2627/) - Andrew Borodin also expressed the idea to extend pageinspect to allow seeing the content of SLRUs - a more specific thing: allow seeing lastOverflowedXid somehow (via SQL or in logs) - we see how important it for standbys health, but we cannot see it now. Any ideas in the direction of observability? Nik >
