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Re: Add Pipelining support in psql

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: "a.kozhemyakin" <a.kozhemyakin@postgrespro.ru>
Cc: Daniel Verite <daniel@manitou-mail.org>, Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>, Jelte Fennema-Nio <postgres@jeltef.nl>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2025-04-22T00:06:20Z
Lists: pgsql-hackers 
On Mon, Apr 21, 2025 at 03:22:28PM +0900, Michael Paquier wrote:
> Anyway, I don't think that there is much we can do under a
> PGRES_FATAL_ERROR in this code path when discarding the pipe results.
> As far as I can tell, the server has failed the query suddenly and the
> whole pipeline flow is borked.  The best thing that I can think of is
> to discard all the results while decrementing the counters, then let
> psql complain about that like in the attached.  I've added two tests
> in TAP, as these trigger a FATAL in the backend so we cannot use the
> normal SQL route, so as we have some coverage.
> 
> @Anthonin: Any thoughts or comments, perhaps?  A second opinion would
> be welcome here.

While considering more ways to test this patch, I've recalled that
injection points that issue a FATAL in the backend to emulate the
original failure with more query patterns can provide more coverage,
and the discard cleanup is showing stable enough as presented in the
patch.  I am wondering if we could not be smarter with the handling of
the counters, but I really doubt that there is much more we can do
under a PGRES_FATAL_ERROR.
--
Michael

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. psql: Fix assertion failures with pipeline mode

  2. psql: Rework TAP routine psql_fails_like() to define WAL sender context

  3. psql: Split extended query protocol meta-commands in --help=commands

  4. psql: Improve descriptions of \\flush[request] in --help

  5. psql: Fix incorrect status code returned by \getresults

  6. psql: Allow queries terminated by semicolons while in pipeline mode

  7. psql: Add \sendpipeline to send query buffers while in a pipeline

  8. psql: Fix memory leak with \gx used within a pipeline

  9. psql: Add pipeline status to prompt and some state variables

  10. Add more tests for utility commands in pipelines

  11. psql: Add support for pipelines

  12. Add braces for if block with large comment in psql's common.c