| From: | Kim Rose Carlsen <krc(at)hiper(dot)dk> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Equivalence Classes when using IN |
| Date: | 2017-10-10 06:52:28 |
| Message-ID: | VI1PR05MB1709ABD41EFF09E4FAAFF4C3C7750@VI1PR05MB1709.eurprd05.prod.outlook.com |
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| Thread: | |
| Lists: | pgsql-general |
> If the only reason that is_simple_subquery() rejects subqueries with
> ORDER BY is due to wanting to keep the order by of a view, then
> couldn't we make is_simple_subquery() a bit smarter and have it check
> if the subquery is going to be joined to something else, which likely
> would destroy the order, or at least it would remove any guarantees of
> it.
>
> Something like the attached?
I dont know if it makes any difference that the ORDER BY is used in a
DISTINCT ON clause. In this case the ORDER BY is important.
- Kim
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