From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Paul Jungwirth <pj(at)illuminatedcomputing(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Are multiple array_aggs going to be in the same order? |
Date: | 2017-04-10 19:19:40 |
Message-ID: | 734.1491851980@sss.pgh.pa.us |
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Lists: | pgsql-general |
Paul Jungwirth <pj(at)illuminatedcomputing(dot)com> writes:
> On 04/10/2017 11:35 AM, Tom Lane wrote:
>> I'm not very keen on recommending that the OP insert an ORDER BY into
>> each aggregate call, because that would cause a separate sort for each
>> aggregate (unless someone's improved that recently while I wasn't
>> looking).
> I mentioned this in my other email, upon a second look I was misreading
> the EXPLAIN output. (The sort was for the GROUP BY, not the individual
> ORDER BYs.) Do aggregate function sorts even show up in EXPLAIN?
They don't. It's not a plannable behavior, just something that's
hard-wired into nodeAgg.c. I'd like to see that improved someday,
but I don't think it's really high on anyone's priority list.
regards, tom lane
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