Hi, On April 2, 2020 9:36:32 AM PDT, Kevin Grittner <kgri...@gmail.com> wrote: >On Wed, Apr 1, 2020 at 7:17 PM Andres Freund <and...@anarazel.de> >wrote: > >> FWIW, with autovacuum=off the query does not get killed until a >manual >> vacuum, nor if fewer rows are deleted and the table has previously >been >> vacuumed. >> >> The vacuum in the second session isn't required. There just needs to >be >> something consuming an xid, so that oldSnapshotControl->latest_xmin >is >> increased. A single SELECT txid_current(); or such in a separate >session >> is sufficient. >> > >Agreed. I don't see that part as a problem; if no xids are being >consumed, >it's hard to see how we could be heading into debilitating levels of >bloat, >so there is no need to perform the early pruning. It would not be >worth >consuming any cycles to ensure that pruning happens sooner than it does >in >this case. It's OK for it to happen any time past the moment that the >snapshot hits the threshold, but it's also OK for it to wait until a >vacuum >of the table or until some activity consumes an xid.
The point about txid being sufficient was just about simplifying the reproducer for wrong query results. Andres -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
