On Tue, Apr 3, 2018 at 10:19 AM, Claudio Freire <klaussfre...@gmail.com> wrote: > On Thu, Mar 29, 2018 at 2:09 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Claudio Freire <klaussfre...@gmail.com> writes: >>> On Wed, Mar 28, 2018 at 6:54 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>>> After 0001, >>>> there's no reason to assume that vacuum is particularly likely to get >>>> cancelled between having made cleanups and having updated the upper FSM >>>> levels. (Maybe the odds are a bit more for the no-indexes case, but >>>> that doesn't seem like it's common enough to justify a special mechanism >>>> either.) >> >>> Why not? >> >>> Any kind of DDL (even those that don't rewrite the heap) would cancel >>> autovacuum. >> >>> You might think DDL isn't common enough to worry about, but I've seen >>> cases where regular reindex were required to keep index bloat in check >>> (and were cron'd), and those cancel autovacuum all the time. >> >> If you've got a situation where every vacuum gets canceled partway >> through, you've got bloat problems regardless, because the heap tuples are >> never getting removed in the first place; worrying about whether the FSM >> is up to date is pretty pointless. The 0001 patch basically updates the >> FSM as soon as it can after the tuples are actually deleted, so I think >> we've made the window as small as practical, and I don't really see a need >> to do extra work (and add substantial extra complexity) to deal with >> missed cleanup a bit sooner. >> >> People who are dealing with this sort of scenario a lot might be well >> advised to reduce autovacuum's maintenance_work_mem, so that the cleanup >> cycles happen more often. That's kind of costly in terms of the number >> of index scans, but it reduces the amount of cleanup work that can be >> lost to a cancel. >> >> (I'd also argue that a setup such as you describe is very possibly making >> things worse not better. Perhaps the 0001 patch will go some way towards >> making it less necessary to do that.) > > Alright, so we just drop 2.
So, that's it then. Thanks
