On Thursday 10 February 2005 03:09 pm, Darcy Buskermolen wrote: > On February 10, 2005 10:58 am, Tom Lane wrote: > > Chris Kratz <[EMAIL PROTECTED]> writes: > > > Does anyone have any idea why there be over a 4s difference between > > > running the statement directly and using explain analyze? > > > > > > Aggregate (cost=9848.12..9848.12 rows=1 width=0) (actual > > > time=4841.231..4841.235 rows=1 loops=1) > > > -> Seq Scan on answer (cost=0.00..8561.29 rows=514729 width=0) > > > (actual time=0.011..2347.762 rows=530576 loops=1) > > > Total runtime: 4841.412 ms > > > > EXPLAIN ANALYZE's principal overhead is two gettimeofday() kernel calls > > per plan node execution, so 1061154 such calls here. I infer that > > gettimeofday takes about 4 microseconds on your hardware ... which seems > > a bit slow for modern machines. What sort of box is it? > > dvl reported the same thing on #postgresql some months back, and neilc > was/is/did looking into it. I belive he came up with a way to move the > function call outside of the loop with no ill effects to the rest of the > expected behavior.
That's interesting to know. It's not a big deal, we were just curious as to why the difference. Tom's explanation makes good sense. We run into the same situation with using a profiler on an application, ie measuring incurs overhead. -Chris ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly