Re: [Proposal] Global temporary tables

> 2020年2月5日 上午4:57，Robert Haas <robertmhaas@gmail.com> 写道：
>
> On Sat, Feb 1, 2020 at 11:14 AM 曾文旌(义从) <wenjing.zwj@alibaba-inc.com> wrote:
>> As global_private_temp-8.patch, think about:
>> 1 session X tale several hours doing some statistical work with the GTT A, which generated some data using
transaction100, The work is not over. 
>> 2 Then session Y vacuumed A, and the GTT's relfrozenxid (in pg_class) was updated to 1000 0000.
>> 3 Then the aotuvacuum happened, the clog  before 1000 0000 was cleaned up.
>> 4 The data in session A could be lost due to missing clog, The analysis task failed.
>>
>> However This is likely to happen because you allowed the GTT do vacuum.
>> And this is not a common problem, that not happen with local temp tables.
>> I feel uneasy about leaving such a question. We can improve it.
>
> Each session is going to need to maintain its own notion of the
> relfrozenxid and relminmxid of each GTT to which it is attached.
> Storing the values in pg_class makes no sense and is completely
> unacceptable.
Yes, I've implemented it in global_temporary_table_v10-pg13.patch

>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company