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.
--
Michael