Re: [Proposal] Global temporary tables

čt 30. 1. 2020 v 15:21 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
napsal:

>
>
> čt 30. 1. 2020 v 15:17 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com>
> napsal:
>
>>
>>
>> > 2020年1月29日 下午9:48，Robert Haas <robertmhaas(at)gmail(dot)com> 写道：
>> >
>> > On Tue, Jan 28, 2020 at 12:12 PM 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com>
>> wrote:
>> >>> Opinion by Pavel
>> >>> + rel->rd_islocaltemp = true; <<<<<<< if this is valid, then the
>> name of field "rd_islocaltemp" is not probably best
>> >>> I renamed rd_islocaltemp
>> >>
>> >> I don't see any change?
>> >>
>> >> Rename rd_islocaltemp to rd_istemp in
>> global_temporary_table_v8-pg13.patch
>> >
>> > In view of commit 6919b7e3294702adc39effd16634b2715d04f012, I think
>> > that this has approximately a 0% chance of being acceptable. If you're
>> > setting a field in a way that is inconsistent with the current use of
>> > the field, you're probably doing it wrong, because the field has an
>> > existing purpose to which new code must conform. And if you're not
>> > doing that, then you don't need to rename it.
>> Thank you for pointing it out.
>> I've rolled back the rename.
>> But I still need rd_localtemp to be true, The reason is that
>> 1 GTT The GTT needs to support DML in read-only transactions ,like local
>> temp table.
>> 2 GTT does not need to hold the lock before modifying the index buffer
>> ,also like local temp table.
>>
>> Please give me feedback.
>>
>
> maybe some like
>
> rel->rd_globaltemp = true;
>
> and somewhere else
>
> if (rel->rd_localtemp || rel->rd_globaltemp)
> {
> ...
> }
>
>
I tested this patch again and I am very well satisfied with behave.

what doesn't work still - TRUNCATE statement

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.

Regards

Pavel

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