| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Amit Kapila <akapila(at)postgresql(dot)org>, pgsql-committers <pgsql-committers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: pgsql: Add a new GUC and a reloption to enable inserts in parallel-mode |
| Date: | 2021-03-25 18:15:19 |
| Message-ID: | CA+TgmoY8kwGi3ZYc0dcqU-m3YOgkzwqeiLfyd1YXLtHYwT14GA@mail.gmail.com |
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| Lists: | pgsql-committers |
On Thu, Mar 25, 2021 at 5:08 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> Wouldn't we need to invalidate the hash entries as soon as something
> parallel-unsafe is associated with them?
Yes.
> If so, how is this better
> than setting a flag in relcache?
You can't legally access a flag in the relcache without taking a
relation lock. If it's possible to avoid that requirement by doing
this some other way, it would be a big win. I'm not sure whether it is
or exactly what would be involved, but relying on the relcache/sinval
interaction surely won't work.
Also, it would address the concern Takayuki-san raised about having to
recompute this in each session. I don't think it would be worth doing
for that reason alone, but it could be a side benefit.
--
Robert Haas
EDB: http://www.enterprisedb.com
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