On Mon, Jul 20, 2020 at 10:14 PM Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > > On 2020-Jul-20, Dilip Kumar wrote: > > > On Fri, Jul 17, 2020 at 4:16 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > So if the vacuum_tolerate_damage is set then in > > > all the cases in heap_prepare_freeze_tuple where the corrupted xid is > > > detected, it will emit a warning and return that nothing is changed in > > > the tuple and the 'tuple_totally_frozen' will also be set to false. > > > Since we are returning false the caller will not try to freeze such > > > tuple and the tuple_totally_frozen is also set to false so that the > > > page will not be marked to all frozen even if all other tuples in the > > > page are frozen. > > > Robert has mentioned at [1] that we probably should refuse to update > > 'relfrozenxid/relminmxid' when we encounter such tuple and emit > > WARNING instead of an error. > > Isn't this already happening per your description above?
As per the above description, we are avoiding to set the page as all frozen. But the vacrelstats->scanned_pages count has already been increased for this page. Now, right after the lazy_scan_heap, we will update the pg_class tuple with the new FreezeLimit and MultiXactCutoff. > > > I think we shall do that in some cases > > but IMHO it's not a very good idea in all the cases. Basically, if > > the xmin precedes the relfrozenxid then probably we should allow to > > update the relfrozenxid whereas if the xmin precedes cutoff xid and > > still uncommitted then probably we might stop relfrozenxid from being > > updated so that we can stop CLOG from getting truncated. > > I'm not sure I understand 100% what you're talking about here (the first > half seems dangerous unless you misspoke), but in any case it seems a > pointless optimization. I mean, if the heap is corrupted, you can hope > to complete the vacuum (which will hopefully return which *other* tuples > are similarly corrupt) but trying to advance relfrozenxid is a lost > cause. I agree with your point. I think we just need to avoid advancing the relfrozenxid in all such cases. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
