| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: executor relation handling |
| Date: | 2018-10-09 18:27:44 |
| Message-ID: | CA+Tgmob+_wTBX9OYpFkDfZSVSY3go3EU6oA9mF=has8JvHTK+g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Oct 6, 2018 at 2:59 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The reasons why we need locks on tables not physically accessed by the
> query are (a) to ensure that we've blocked, or received sinval messages
> for, any DDL related to views or partition parent tables, in case that
> would invalidate the plan; (b) to allow firing triggers safely, in
> the case of partition parent tables. Neither of these issues apply to
> a parallel worker -- the plan is already frozen before it can ever
> start, and it isn't going to be firing any triggers either.
That last part could *easily* change in a future release. We've
already started to allow CTAS with parallel query, and there have
already been multiple people wanting to allow more. It would be a
shame if we threw up additional obstacles in the way of that...
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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