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Re: [Proposal] Global temporary tables

曾文旌 (义从) <wenjing.zwj@alibaba-inc.com>

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From: 曾文旌(义从) <wenjing.zwj@alibaba-inc.com>
To: 曾文旌(义从) <wenjing.zwj@alibaba-inc.com>, "Pavel Stehule" <pavel.stehule@gmail.com>
Cc: "Robert Haas" <robertmhaas@gmail.com>, "Tomas Vondra" <tomas.vondra@2ndquadrant.com>, "Konstantin Knizhnik" <k.knizhnik@postgrespro.ru>, "PostgreSQL Hackers" <pgsql-hackers@postgresql.org>, 蔡松露(子嘉) <zijia@taobao.com>, Cai, Le <le.cai@alibaba-inc.com>, 萧少聪(铁庵) <shaocong.xsc@alibaba-inc.com>
Date: 2020-02-21T15:40:14Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. PageAddItemExtended(): Add LP_UNUSED assertion.

  2. Remove temporary files after backend crash

  3. Fix comment in indexing.c

  4. Fix failure to ignore leftover temp tables after a server crash.

Hi,
I have started testing the "Global temporary table" feature,
That's great, I see hope.
from "gtt_v11-pg13.patch". Below is my findings:

-- session 1:
postgres=# create global temporary table gtt1(a int);
CREATE TABLE

-- seeeion 2:
postgres=# truncate gtt1 ;
ERROR:  could not open file "base/13585/t3_16384": No such file or directory

is it expected?

Oh ,this is a bug, I fixed it.

Wenjing


On Sun, Feb 16, 2020 at 8:53 PM Pavel Stehule <pavel.stehule@gmail.com <mailto:pavel.stehule@gmail.com>> wrote:


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


> 2020年2月15日 下午6:06，Pavel Stehule <pavel.stehule@gmail.com <mailto:pavel.stehule@gmail.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 <http://www.enterprisedb.com/>
>> > The Enterprise PostgreSQL Company
>> 
> 



-- 
With Regards,
Prabhat Kumar Sahu
EnterpriseDB: http://www.enterprisedb.com <http://www.enterprisedb.com/>