| From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Vlad Bokov <vlad(at)razum2um(dot)me> |
| Cc: | "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: CREATE AGGREGATE array_cat |
| Date: | 2020-11-19 00:37:26 |
| Message-ID: | d07b415b-232a-3fa1-b6fa-779db621f034@postgresfriends.org |
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| Lists: | pgsql-hackers |
On 11/18/20 11:19 PM, David G. Johnston wrote:
> On Wednesday, November 18, 2020, Vlad Bokov <vlad(at)razum2um(dot)me> wrote:
>
>> Hi, I wonder why there's no function to aggregate arrays by
>> concatenation out of the box?
>>
>
> See array_agg(...)
Why? That doesn't do what is wanted.
vik=# select array_agg(a) from (values (array[1]), (array[2])) as v(a);
array_agg
-----------
{{1},{2}}
(1 row)
vik=# CREATE AGGREGATE array_cat (anyarray)
vik-# (
vik(# sfunc = array_cat,
vik(# stype = anyarray,
vik(# initcond = '{}'
vik(# );
CREATE AGGREGATE
vik=# select array_cat(a) from (values (array[1]), (array[2])) as v(a);
array_cat
-----------
{1,2}
(1 row)
--
Vik Fearing
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