From: | 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com> |
---|---|
To: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
Cc: | "Tomas Vondra" <tomas(dot)vondra(at)2ndquadrant(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: | 2020-01-08 07:03:09 |
Message-ID: | C7912E33-294F-4DFC-9CCC-5570590605C4@alibaba-inc.com |
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Lists: | pgsql-hackers |
> 2020年1月6日 下午8:17,Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> 写道:
>
> 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.
The current patch provides several functions as extension(pg_gtt) for read gtt statistics.
Next I can move them to the kernel and let the view pg_stats can see gtt’s statistics.
> Regards,
> Dean
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