Re: MAP syntax for arrays

From: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
To: 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>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: MAP syntax for arrays
Date: 2018-05-08 14:15:33
Message-ID: 42cf8743-971d-b816-bd24-c17d70167ebf@2ndquadrant.com
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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.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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