| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Do CustomScan as not projection capable node |
| Date: | 2019-04-22 13:40:27 |
| Message-ID: | CA+Tgmobf7GocuuD_KLqKj-pMRGVSxLL8=vsVwXZg_fojG2gkrg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Apr 19, 2019 at 12:45 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I don't buy this for a minute. Where do you think projection is
> going to happen? There isn't any existing node type that *couldn't*
> support projection if we insisted that that be done across-the-board.
> I think it's mostly just a legacy thing that some don't.
I think there may actually be some good reasons for that. If
something like an Append or Material node projects, it seems to me
that this means that we built the wrong tlist for its input(s).
That justification doesn't apply to custom scans, though.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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