| From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, 蔡松露(子嘉) <zijia(at)taobao(dot)com>, "Cai, Le" <le(dot)cai(at)alibaba-inc(dot)com>, 萧少聪(铁庵) <shaocong(dot)xsc(at)alibaba-inc(dot)com> |
| Subject: | Re: [Proposal] Global temporary tables |
| Date: | 2020-01-13 20:12:38 |
| Message-ID: | 20200113201216.GA17684@nol |
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| Lists: | pgsql-hackers |
On Mon, Jan 13, 2020 at 05:32:53PM +0100, Tomas Vondra wrote:
> On Mon, Jan 13, 2020 at 11:08:40AM +0300, Konstantin Knizhnik wrote:
> >
> >"if any code tried to access the statistics directly from the table,
> >rather than via the caches".
> >
> >Currently optimizer is accessing statistic though caches. So this
> >approach works. If somebody will rewrite optimizer or provide own
> >custom optimizer in extension which access statistic directly
> >then it we really be a problem. But I wonder why bypassing catalog
> >cache may be needed.
> >
>
> I don't know, but it seems extensions like hypopg do it.
AFAIR, hypopg only opens pg_statistic to use its tupledesc when creating
statistics on hypothetical partitions, but it should otherwise never reads or
need plain pg_statistic rows.
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