| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | "btober(at)computer(dot)org" <btober(at)broadstripe(dot)net>, Howard News <howardnews(at)selestial(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: select function alias |
| Date: | 2016-11-30 19:21:21 |
| Message-ID: | CAHyXU0z-568VKOEemSW423TK5pFYxKoZBrBRHZ80hJYJW7htXw@mail.gmail.com |
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| Lists: | pgsql-general |
On Wed, Nov 30, 2016 at 12:15 PM, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> On Wed, Nov 30, 2016 at 8:15 AM, btober(at)computer(dot)org
> <btober(at)broadstripe(dot)net> wrote:
>>
>> 5. Use a CTE:
>>
>> with shortnames as (
>> select to_char(impressions_create_date,'yyyy-mm-dd') as ymd from
>> impressionsdb
>> ) select ymd from shortnames where ymd like '2016-11%';
>>
>
> Except that WHERE clause won't get pushed down (I think...haven't checked an
> explain recently) so a sub-select is definitely better in this scenario.
It's still the case FWICT. I suspect CTE optimization fencing is
mostly considered a feature, not a bug.
merlin
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