Hi Michael,
On Fri, Jul 18, 2025 at 3:01 PM Michael J. Baars <mjbaars1977.pg...@gmail.com> wrote: > > Hello fellow PostgreSQL users and developers, > > I installed a new Fedora release last week and ran into a peculiar problem: > > Each night I need to run computations through about 70.000 rows and using > release 16.3 that took about 4 hours to complete, but using release 16.9 the > same computations now take about 8 hours to complete. > > I've checked the unix sockets, inet sockets and the NVMe drive for deviations > between the different kernels, but found none. Configuration files are > exactly identical as well. Somewhere in between release 16.3 and release > 16.9, changes must have been implemented that make the execution engine about > two times slower than it was. > > Two particular queries, that run about 70.000 times each night, gave the > following results: > > Query 1 over unix sockets: > > release 16.3: > Time: 194.093 ms > Time: 169.714 ms > Time: 174.424 ms > Time: 170.285 ms > > release 16.9: > Time: 281.554 ms > Time: 290.257 ms > Time: 290.886 ms > Time: 287.528 ms > > Query 2 over unix sockets: > > release 16.3: > Time: 132.500 ms > Time: 133.182 ms > Time: 134.511 ms > Time: 130.818 ms > > release 16.9: > Time: 251.238 ms > Time: 247.749 ms > Time: 246.862 ms > Time: 248.541 ms > > These differences add up to about 4 hours additional computation time each > night. Apparently I have to scale down on the amount of work that can be done > in one night. Can you please provide "explain analyze" output of both the queries across both releases for investigation. -- Best Wishes, Ashutosh Bapat
