On Sat, Mar 21, 2020 at 8:35 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Anders Steinlein <and...@e5r.no> writes: > > So I don't understand this big difference? Because it does seem like > citext > > is indeed the difference. > > It seems odd to me too. I'm not at all surprised that citext comparison > is way slower than text, but I am surprised that you don't see that on 9.4 > as well.
Indeed. But also, how come this is part of the planner time? I would think that would be part of the execution time? (Just a detail I'm curious about.) Is lc_ctype the same in both installs? Yes, lc_ctype is also nb_NO.UTF-8 on both installs. > For that matter, is the underlying libc the same? We have seen large > performance discrepancies > between different libc versions in this area. > This they most definitely are not. 9.4 was running on an old box, Ubuntu 12.04, while 12 is on an up-to-date Ubuntu 18.04 LTS. AFAICS, 2.15 on the 9.4 box and 2.27 on the 12 box. If you're interested in digging further, getting a "perf" profile while > running the problem query over and over would likely yield some insight > about where the time is going. > I collected a profile now, but I've never done this before so I'm unsure how to read the report. I'll email you directly with a link to the perf.data file, if you would be so kind as to take a quick look. From what little I think I understand, towlower from libc seems to take up 32% of the total time, although that by itself doesn't seem to explain almost 2 second planner time vs. 20ms... Should really citext/libc string comparison "issues" cause this order of magnitude slower planner time? Best, -- a.
