On Tue, 06 Sep 2022 at 16:17, Daniel Gustafsson <dan...@yesql.se> wrote: >> On 6 Sep 2022, at 10:10, Zhang Mingli <zmlpostg...@gmail.com> wrote: >> On Sep 6, 2022, 16:03 +0800, Japin Li <japi...@hotmail.com>, wrote: > >> It's out-of-date, doesn't it? I'm not sure s/RecentGlobalXmin/RecentXmin/g >> is right. Any thoughts? >> I’m afraid not, RecentGlobalXmin is split to several GlobalVis* variables. >> Need to check one by one. > > It's a set of functions actually and not variables IIRC. > > It's worth looking at the entire comment and not just the grep output though, > as these three places share the exact same comment. Note the second > paragraph: > > /* > * Start a new transaction here before first access to db, and get a > * snapshot. We don't have a use for the snapshot itself, but we're > * interested in the secondary effect that it sets RecentGlobalXmin. (This > * is critical for anything that reads heap pages, because HOT may decide > * to prune them even if the process doesn't attempt to modify any > * tuples.) > * > * FIXME: This comment is inaccurate / the code buggy. A snapshot that is > * not pushed/active does not reliably prevent HOT pruning (->xmin could > * e.g. be cleared when cache invalidations are processed). > */ > > This was added in dc7420c2c92 which removed RecentGlobalXmin, addressing that > FIXME would of course be very welcome.
My bad! Thanks for pointing out this. -- Regrads, Japin Li. ChengDu WenWu Information Technology Co.,Ltd.
