| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
| Cc: | Chapman Flack <chap(at)anastigmatix(dot)net>, Ildar Musin <i(dot)musin(at)postgrespro(dot)ru>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: MAP syntax for arrays |
| Date: | 2018-05-08 14:18:06 |
| Message-ID: | 20180508141806.io5jtovdjqxydbrv@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Peter Eisentraut wrote:
> On 5/8/18 09:19, Chapman Flack wrote:
> > On 05/08/2018 08:57 AM, Ildar Musin wrote:
> >>
> >> select map (pow(2, x) - 1 for x in array[1,2,3,4,5]);
> >
> > I wonder how efficient an implementation would be possible strictly
> > as a function, without grammar changes?
>
> Yeah, you can pass a function to another function (using regprocedure or
> just oid), so this should be possible entirely in user space.
How would you invoke it? It seems you'd be forced to use EXECUTE in a
plpgsql function, or a C function.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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