Re: [Proposal] Global temporary tables

ne 16. 2. 2020 v 16:15 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com>
napsal:

>
>
> 2020年2月15日 下午6:06，Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> 写道：
>
>
> postgres=# insert into foo select generate_series(1,10000);
>> INSERT 0 10000
>> postgres=# \dt+ foo
>> List of relations
>> ┌────────┬──────┬───────┬───────┬─────────────┬────────┬─────────────┐
>> │ Schema │ Name │ Type │ Owner │ Persistence │ Size │ Description │
>> ╞════════╪══════╪═══════╪═══════╪═════════════╪════════╪═════════════╡
>> │ public │ foo │ table │ pavel │ session │ 384 kB │ │
>> └────────┴──────┴───────┴───────┴─────────────┴────────┴─────────────┘
>> (1 row)
>>
>> postgres=# truncate foo;
>> TRUNCATE TABLE
>> postgres=# \dt+ foo
>> List of relations
>> ┌────────┬──────┬───────┬───────┬─────────────┬───────┬─────────────┐
>> │ Schema │ Name │ Type │ Owner │ Persistence │ Size │ Description │
>> ╞════════╪══════╪═══════╪═══════╪═════════════╪═══════╪═════════════╡
>> │ public │ foo │ table │ pavel │ session │ 16 kB │ │
>> └────────┴──────┴───────┴───────┴─────────────┴───────┴─────────────┘
>> (1 row)
>>
>> I expect zero size after truncate.
>>
>> Thanks for review.
>>
>> I can explain, I don't think it's a bug.
>> The current implementation of the truncated GTT retains two blocks of FSM
>> pages.
>> The same is true for truncating regular tables in subtransactions.
>> This is an implementation that truncates the table without changing the
>> relfilenode of the table.
>>
>>
> This is not extra important feature - now this is little bit a surprise,
> because I was not under transaction.
>
> Changing relfilenode, I think, is necessary, minimally for future VACUUM
> FULL support.
>
> Not allowing relfilenode changes is the current limit.
> I think can improve on it. But ,This is a bit complicated.
> so I'd like to know the necessity of this improvement.
> Could you give me more details?
>

I don't think so GTT without support of VACUUM FULL can be accepted. Just
due consistency.

Regards

Pavel

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