| From: | Loïc Revest <l(dot)revest(at)apc(dot)fr> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: lag() default value ignored for some window partition depending on table records count? |
| Date: | 2022-04-27 15:19:30 |
| Message-ID: | CABkOrLsPtG=fgHTuTQz35RMx1jvFJ8NN1Nrvto-b4hQB8hS5oQ@mail.gmail.com |
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| Lists: | pgsql-bugs |
>> On Wed, 27 Apr 2022 at 10:48, David G. Johnston
>> <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>>
>> There can only be qual pushdown when the column in the qual is present
>> in the PARTITION BY clause. In this case, there's no PARTITION BY
>> clause, so can't be pushdowns.
>>
peer_id being only used as a sort criterion instead of the
partitioning factor is indeed the culprit, and a true shame I haven't
figured it out on my own.
lag(<value>, 1, 0::numeric) OVER (PARTITION BY peer_id ORDER BY
calculation_time) returns 0::numeric for first row in partition, as
expected.
Thanks a lot to all three of you for pointing it out to me, and my
apologies for the unrelevant noise on that list.
Regards,
L. Revest
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