Re: [Proposal] Global temporary tables

Hi

so 11. 1. 2020 v 15:00 odesílatel 曾文旌(义从) <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).

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.

Todo:

pg_table_size function doesn't work

Regards

Pavel

> Wenjing
>
>
>
>
>
> 2020年1月6日 上午4:06，Tomas Vondra <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/
>
> [2] 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
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
>
>