Re: Asynchronous Append on postgres_fdw nodes.

Andrei Lepikhov <a.lepikhov@postgrespro.ru>

From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>

To: Etsuro Fujita <etsuro.fujita@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>

Cc: Justin Pryzby <pryzby@telsasoft.com>, "movead.li" <movead.li@highgo.ca>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2020-10-08T11:40:24Z

Lists: pgsql-hackers

Attachments

0001-async_capable_subqueries.patch (text/x-patch)

Hi,
I want to suggest one more improvement. Currently the
is_async_capable_path() routine allow only ForeignPath nodes as async 
capable path. But in some cases we can allow SubqueryScanPath as async 
capable too.

For example:
SELECT * FROM ((SELECT * FROM foreign_1)
UNION ALL
(SELECT a FROM foreign_2)) AS b;

is async capable, but:

SELECT * FROM ((SELECT * FROM foreign_1 LIMIT 10)
UNION ALL
(SELECT a FROM foreign_2 LIMIT 10)) AS b;

doesn't async capable.

The patch in attachment tries to improve this situation.

-- 
regards,
Andrey Lepikhov
Postgres Professional

Commits

Improve comments for trivial_subqueryscan().
- 4a8a5dd7f59c 15.0 landed
Disable asynchronous execution if using gating Result nodes.
- ebb790241523 14.3 landed
- 5c854e7a2c8a 15.0 landed
Allow asynchronous execution in more cases.
- c2bb02bc2e85 15.0 landed
Doc: Further update documentation for asynchronous execution.
- eab81953682d 14.0 landed
Fix rescanning of async-aware Append nodes.
- f3baaf28a6da 14.0 landed
Doc: Update documentation for asynchronous execution.
- 15fcd33e0694 14.0 landed
Fix EXPLAIN ANALYZE for async-capable nodes.
- a363bc6da96b 14.0 landed
Minor code cleanup in asynchronous execution support.
- bb684c82f733 14.0 landed
Adjust input value to WaitEventSetWait() in ExecAppendAsyncEventWait().
- a8af856d3257 14.0 landed
Add support for asynchronous execution.
- 27e1f14563cf 14.0 landed