Re: [Proposal] Global temporary tables

> 2020年1月14日 下午9:20，Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> 写道：
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> út 14. 1. 2020 v 14:09 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com <mailto:wenjing(dot)zwj(at)alibaba-inc(dot)com>> napsal:
> 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 <mailto: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
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>>
>> Please give me feedback.
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>> I tested the functionality
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>> 1. i think so "ON COMMIT PRESERVE ROWS" should be default mode (like local temp tables).
> makes sense, I will fix it.
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>> I tested some simple scripts
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>> test01.sql
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>> 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
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>> after 100 sec, the table pg_attribute has 3.2MB
>> and 64 tps, 6446 transaction
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>> test02.sql
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>> 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.
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>> From my perspective, this functionality is great.
> Yes, frequent ddl causes catalog bloat, GTT avoids this problem.
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>> Todo:
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>> 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) .
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> It's question how much GTT tables should be similar to classic tables. But the reporting in psql should to work \dt+, \l+, \di+

I have fixed this problem.

Please let me know where I need to improve.

Thanks

Wenjing

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>> Regards
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>> Pavel
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>>
>> Wenjing
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>>> 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
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