Horton

Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: Jacob Champion <jacob.champion@enterprisedb.com>, Tom Lane <tgl@sss.pgh.pa.us>, Denis Laxalde <denis.laxalde@dalibo.com>, vignesh C <vignesh21@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Greg Stark <stark@mit.edu>, "Gregory Stark (as CFM)" <stark.cfm@gmail.com>, Jelte Fennema <Jelte.Fennema@microsoft.com>, Daniel Gustafsson <daniel@yesql.se>, Peter Eisentraut <peter@eisentraut.org>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2024-03-14T10:33:30Z
Lists: pgsql-hackers 
On 2024-Mar-14, Jelte Fennema-Nio wrote:

> On Wed, 13 Mar 2024 at 20:08, Jacob Champion
> <jacob.champion@enterprisedb.com> wrote:
> > I hit this on my machine. With the attached diff I can reproduce
> > constantly (including with the most recent test patch); I think the
> > cancel must be arriving between the bind/execute steps?
> 
> Nice find! Your explanation makes total sense. Attached a patchset
> that fixes/works around this issue by using the simple query protocol
> in the cancel test.

Hmm, isn't this basically saying that we're giving up on reliably
canceling queries altogether?  I mean, maybe we'd like to instead fix
the bug about canceling queries in extended query protocol ...
Isn't that something you're worried about?

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"World domination is proceeding according to plan"        (Andrew Morton)

Commits

  1. postgres_fdw: re-issue cancel requests a few times if necessary.

  2. Make postgres_fdw's query_cancel test less flaky.

  3. postgres_fdw: Split out the query_cancel test to its own file

  4. Fix copy-paste mistake in PQcancelCreate

  5. Make libpqsrv_cancel's return const char *, not char *

  6. Stabilize postgres_fdw test

  7. libpq-be-fe-helpers.h: wrap new cancel APIs

  8. dblink/isolationtester/fe_utils: Use new cancel API

  9. Put libpq_pipeline cancel test back

  10. Hopefully make libpq_pipeline's new cancel test more reliable

  11. libpq: Add encrypted and non-blocking query cancellation routines

  12. libpq: Move pg_cancel to fe-cancel.c

  13. Add tests for libpq query cancellation APIs

  14. Add missing connection statuses to docs

  15. libpq: Change some static functions to extern

  16. libpq: Add pqReleaseConnHosts function

  17. libpq: Move cancellation related functions to fe-cancel.c

  18. Make spelling of cancelled/cancellation consistent

  19. Be more wary about OpenSSL not setting errno on error.

  20. libpq: Use modern socket flags, if available.

  21. Drop test view when done with it.

  22. Doc: add some doco about using the libpq_pipeline test module.

  23. postgres_fdw: Allow cancellation of transaction control commands.