Magnus Hagander <magnus@hagander.net> writes: > On Tue, Sep 8, 2020 at 4:38 PM Tom Lane <tgl@sss.pgh.pa.us> wrote: >> The reason that's not so is that whether or not transaction A *has* >> touched table B is irrelevant. It *could* read table B at any moment, >> for all autovacuum knows. Therefore we cannot remove rows that should >> still be visible to A's snapshot.
> Right. But in the default isolation level, the snapshot of A gets reset > between each SELECT, and does not persist to the end of the transaction.
Well, we don't know what isolation level the OP is using. We also don't
Per the thread, he's using the default, which should be read committed.
know what PG version he's using. From memory, it hasn't been that long
Per his session list, 11.2.
since we fixed things so that an idle read-committed transaction advertises no xmin. It's also possible that the transaction isn't really idle between statements (eg, if it's holding open cursors, or the like).
Oh, now *cursors* is definitely something I didn't think of. And especially in the context of ODBC, I wonder if it might be creating cursors transparently, and that this somehow causes the problems.
Michael, do you know if that might be the case? Or try enabling log_statements to check if it is?