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Subject: Re: Add Pipelining support in psql
From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Anthonin Bonnefoy" <anthonin.bonnefoy@datadoghq.com>
Cc: Michael Paquier <michael@paquier.xyz>,
 Jelte Fennema-Nio <postgres@jeltef.nl>,
 PostgreSQL Hackers <pgsql-hackers@postgresql.org>
In-Reply-To: <CAO6_XqrrjJRhKNhYa9Cg=_BSH8MmS1tAHMFq-H7fH=NcWJ-jvw@mail.gmail.com>
Date: Fri, 28 Feb 2025 17:31:00 +0100
Message-Id: <ad4b9f1a-f7fe-4ab8-8546-90754726d0be@manitou-mail.org>
Archived-At: <https://www.postgresql.org/message-id/ad4b9f1a-f7fe-4ab8-8546-90754726d0be%40manitou-mail.org>
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	Anthonin Bonnefoy wrote:

> > What is the reasoning here behind this restriction?  \gx is a wrapper
> > of \g with expanded mode on, but it is also possible to call \g with
> > expanded=3Don, bypassing this restriction.
>=20
> The issue is that \gx enables expanded mode for the duration of the
> query and immediately reset it in sendquery_cleanup. With pipelining,
> the command is piped and displaying is done by either \endpipeline or
> \getresults, so the flag change has no impact. Forbidding it was a way
> to make it clearer that it won't have the expected effect

But it's not just \gx

The following invocations don't respect the desired output destination
and formats (ignoring them), when a pipeline is active:

select ... \bind \g filename
select ... \bind \g |program
select ... \bind \g (format=3Dunaligned tuples_only=3Don)

Just like for \gx the problem is that in a pipeline, sending the query
is not followed by getting the results, and the output properties
of a query are lost in between.


Best regards,
--=20
Daniel V=E9rit=E9=20
https://postgresql.verite.pro/