Re: [Proposal] Global temporary tables

Thank you for review my patch.

> 2020年1月12日 上午4:27，Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> 写道：
>
> Hi
>
> so 11. 1. 2020 v 15:00 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com <mailto:wenjing(dot)zwj(at)alibaba-inc(dot)com>> napsal:
> Hi all
>
> This is the latest patch
>
> The updates are as follows:
> 1. Support global temp Inherit table global temp partition table
> 2. Support serial column in GTT
> 3. Provide views pg_gtt_relstats pg_gtt_stats for GTT’s statistics
> 4. Provide view pg_gtt_attached_pids to manage GTT
> 5. Provide function pg_list_gtt_relfrozenxids() to manage GTT
> 6. Alter GTT or rename GTT is allowed under some conditions
>
>
> Please give me feedback.
>
> I tested the functionality
>
> 1. i think so "ON COMMIT PRESERVE ROWS" should be default mode (like local temp tables).
makes sense, I will fix it.

>
> I tested some simple scripts
>
> test01.sql
>
> CREATE TEMP TABLE foo(a int, b int);
> INSERT INTO foo SELECT random()*100, random()*1000 FROM generate_series(1,1000);
> ANALYZE foo;
> SELECT sum(a), sum(b) FROM foo;
> DROP TABLE foo; -- simulate disconnect
>
>
> after 100 sec, the table pg_attribute has 3.2MB
> and 64 tps, 6446 transaction
>
> test02.sql
>
> INSERT INTO foo SELECT random()*100, random()*1000 FROM generate_series(1,1000);
> ANALYZE foo;
> SELECT sum(a), sum(b) FROM foo;
> DELETE FROM foo; -- simulate disconnect
>
>
> after 100 sec, 1688 tps, 168830 transactions
>
> So performance is absolutely different as we expected.
>
> From my perspective, this functionality is great.
Yes, frequent ddl causes catalog bloat, GTT avoids this problem.

>
> Todo:
>
> pg_table_size function doesn't work
Do you mean that function pg_table_size() need get the storage space used by the one GTT in the entire db(include all session) .

>
> Regards
>
> Pavel
>
>
> Wenjing
>
>
>
>
>
>> 2020年1月6日 上午4:06，Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com <mailto:tomas(dot)vondra(at)2ndquadrant(dot)com>> 写道：
>>
>> Hi,
>>
>> I think we need to do something with having two patches aiming to add
>> global temporary tables:
>>
>> [1] https://commitfest.postgresql.org/26/2349/ <https://commitfest.postgresql.org/26/2349/>
>>
>> [2] https://commitfest.postgresql.org/26/2233/ <https://commitfest.postgresql.org/26/2233/>
>>
>> As a reviewer I have no idea which of the threads to look at - certainly
>> not without reading both threads, which I doubt anyone will really do.
>> The reviews and discussions are somewhat intermixed between those two
>> threads, which makes it even more confusing.
>>
>> I think we should agree on a minimal patch combining the necessary/good
>> bits from the various patches, and terminate one of the threads (i.e.
>> mark it as rejected or RWF). And we need to do that now, otherwise
>> there's about 0% chance of getting this into v13.
>>
>> In general, I agree with the sentiment Rober expressed in [1] - the
>> patch needs to be as small as possible, not adding "nice to have"
>> features (like support for parallel queries - I very much doubt just
>> using shared instead of local buffers is enough to make it work.)
>>
>> regards
>>
>> --
>> Tomas Vondra http://www.2ndQuadrant.com <http://www.2ndquadrant.com/>
>> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>