| From: | andres(at)anarazel(dot)de (Andres Freund) |
|---|---|
| To: | Craig James <cjames(at)emolecules(dot)com> |
| Cc: | Merlin Moncure <mmoncure(at)gmail(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, "Graeme B(dot) Bell" <graeme(dot)bell(at)nibio(dot)no>, postgres performance list <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Hmmm... why does CPU-intensive pl/pgsql code parallelise so badly when queries parallelise fine? Anyone else seen this? |
| Date: | 2015-07-08 22:45:18 |
| Message-ID: | 20150708224518.GT10242@alap3.anarazel.de |
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| Lists: | pgsql-performance |
On 2015-07-08 15:38:24 -0700, Craig James wrote:
> From my admittedly naive point of view, it's hard to see why any of this
> matters. I have functions that do purely CPU-intensive mathematical
> calculations ... you could imagine something like is_prime(N) that
> determines if N is a prime number. I have eight clients that connect to
> eight backends. Each client issues an SQL command like, "select
> is_prime(N)" where N is a simple number.
I mostly replied to Merlin's general point (additionally in the context of
plpgsql).
But I have a hard time seing that postgres would be the bottleneck for a
is_prime() function (or something with similar characteristics) that's
written in C where the average runtime is more than, say, a couple
thousand cyles. I'd like to see a profile of that.
Andres
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