On Mon, 20 Feb 2023 at 10:18, Tom Lane <tgl@sss.pgh.pa.us> wrote: > I don't see it at all. Comparing your two test queries on released > branches, I see maybe 2x penalty for the ORDER BY NULL, not 30x. > (In HEAD there's only about 13% penalty.) I wonder what PG version > you are testing.
I suspect ed1a88dda would be what made this faster in master. We'll check for peer rows to check "NULL IS NOT DISTINCT FROM NULL" prior to that change with the ORDER BY NULL query.
yes, I tested it on master, and the query is little bit slower still, but not too much (27 sec x 24 sec)
