On Sat, Jan 09, 2021 at 08:25:39PM +0500, Andrey Borodin wrote: > > 9 янв. 2021 г., в 15:17, Noah Misch <n...@leadboat.com> написал(а):
> >> I'm a little bit afraid that this kind of patch can hide bugs (while > >> potentially saving some users data). Besides this patch seems like a > >> useful precaution. Maybe we could emit scary warnings if SLRU segments do > >> not stack into continuous range? > > > > Scary warnings are good for an observation that implies a bug, but the > > slru-truncate-t-insurance patch causes such an outcome in non-bug cases > > where > > it doesn't happen today. In other words, discontinuous ranges of SLRU > > segments would be even more common after that patch. For example, it would > > happen anytime oldestXID advances by more than ~1B at a time. > > Uhm, I thought that if there is going to be more than ~1B xids - we are going > to keep all segements forever and range still will be continuous. Or am I > missing something? No; it deletes the most recent ~1B and leaves the older segments. An exception is multixact, as described in the commit message and the patch's change to a comment in TruncateMultiXact().
