| From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, 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: | 2020-01-06 12:17:43 |
| Message-ID: | CAEZATCW0omTuLCNnPym4F8GMLBX-WZpAS3FpZyU06mkHPoOi_g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, 6 Jan 2020 at 11:01, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>
> On Mon, Jan 06, 2020 at 01:04:15PM +0800, 曾文旌(义从) wrote:
>
> >2 We feel that gtt needs to maintain statistics, but there is no
> >agreement on what it will be done.
> >
>
> I certainly agree GTT needs to maintain statistics, otherwise it'll lead
> to poor query plans.
+1
> AFAIK the current patch stores the info in a hash
> table in a backend private memory, and I don't see how else to do that
> (e.g. storing it in a catalog would cause catalog bloat).
>
It sounds like it needs a pair of system GTTs to hold the table and
column statistics for other GTTs. One would probably have the same
columns as pg_statistic, and the other just the relevant columns from
pg_class. I can see it being useful for the user to be able to see
these stats, so perhaps they could be UNIONed into the existing stats
view.
Regards,
Dean
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