From: | 曾文旌 <wenjing(dot)zwj(at)alibaba-inc(dot)com> |
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To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Prabhat Sahu <prabhat(dot)sahu(at)enterprisedb(dot)com>, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, 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: | 2020-04-07 08:57:57 |
Message-ID: | A1BED593-4D6F-429D-8971-55E6EF62314C@alibaba-inc.com |
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Thread: | |
Lists: | pgsql-hackers |
> 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.
HI all
Vacuum full GTT, cluster GTT is already supported in global_temporary_table_v24-pg13.patch.
Wenjing
>
> Regards
>
> Pavel Stehule
>
>
> Wenjing
>
>>
>> Regards
>>
>> Pavel
>>
>>
>>
>> Wenjing
>>
>>
>>
>>
>> >
>> > --
>> > Robert Haas
>> > EnterpriseDB: http://www.enterprisedb.com <http://www.enterprisedb.com/>
>> > The Enterprise PostgreSQL Company
>>
>
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