On Tue, Sep 1, 2020 at 2:19 AM Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > FWIW I suspect some of this difference may be due to logical vs. > physical I/O. iosnoop only tracks physical I/O sent to the device, but > maybe we do much more logical I/O and it simply does not expire from > page cache for the sort. It might behave differently for larger data > set, longer query, ...
There is also the fact that the LogicalTapeSetBlocks() instrumentation is known to have problems that we still need to fix: https://www.postgresql.org/message-id/CAH2-Wzn5PCBLUrrds=hD439LtWP+PD7ekRTd=8ldtqj+ko5...@mail.gmail.com I'm not suggesting that this is a significant factor here. But I can't rule it out just yet either. > I don't know. I certainly understand the desire not to change things > this late. OTOH I'm worried that we'll end up receiving a lot of poor > plans post release. I think that this needs to get fixed before release. -- Peter Geoghegan
