Re: [Proposal] Global temporary tables

2020年1月12日 上午4:27，Pavel Stehule <pavel.stehule@gmail.com> 写道：

Hi

so 11. 1. 2020 v 15:00 odesílatel 曾文旌(义从) <wenjing.zwj@alibaba-inc.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.vondra@2ndquadrant.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