| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Surafel Temesgen <surafel3000(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: FETCH FIRST clause PERCENT option |
| Date: | 2018-08-21 12:50:25 |
| Message-ID: | 20180821125025.u2c6uzqnca3dmt2i@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2018-08-21 15:47:07 +0300, Surafel Temesgen wrote:
> On Thu, Aug 16, 2018 at 5:34 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> >
> > Won't that have rather massive issues with multiple evaluations of
> > clauses in the query? Besides being really expensive?
> >
> The plan re-scane after first execution I can’t see issue for multiple
> execution of a clause in this case
Imagine volatile functions being used. That can be problematic because
of repeated side-effects, but also will lead to plainly wrong
results. Consider what happens with your approach where somebody does
something like WHERE value < random().
Greetings,
Andres Freund
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