On Wed, Dec 30, 2020 at 8:17 PM Michael Paquier <mich...@paquier.xyz> wrote: > On Tue, Dec 29, 2020 at 04:16:06PM -0500, Tom Lane wrote: > > Hmph, no, a look at explain.c shows that the "Execution Time" is just > > based on the difference of INSTR_TIME_SET_CURRENT measurements taken > > within the current process. It's difficult to conclude anything except > > that the clock went backwards. Which is weird, because according to [1] > > that system does have clock_gettime(CLOCK_MONOTONIC), which'd be our > > preferred choice of INSTR_TIME time base; and such clocks are not > > supposed to go backwards ever. > > I was looking at that, and I agree that this looks like a monotonic > clock going backwards. Or could it be possible that it gave 0.0 as > result, still a minus sign was appended? That would mean an execution > that took less than 1us per the system clock.
If I'm reading this right, it might be further evidence of CLOCK_MONOTONIC going backwards on OpenBSD, this time by quite a lot (the regular expression doesn't tolerate a leading minus sign, so the test failed): https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=morepork&dt=2021-11-10%2020%3A51%3A32 # Log entry not matching: 1 22 -124769 0 1636578000 152817
