Re: Asynchronous Append on postgres_fdw nodes.

From: Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>
To: Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, "movead(dot)li" <movead(dot)li(at)highgo(dot)ca>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Asynchronous Append on postgres_fdw nodes.
Date: 2020-10-08 11:40:24
Message-ID: 7fe10f95-ac6c-c81d-a9d3-227493eb9055@postgrespro.ru
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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

Attachment Content-Type Size
0001-async_capable_subqueries.patch text/x-patch 3.0 KB

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