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: Denis Laxalde <denis.laxalde@dalibo.com>, vignesh C <vignesh21@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Greg Stark <stark@mit.edu>, Tom Lane <tgl@sss.pgh.pa.us>, "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: 2024-03-12T16:50:48Z
Lists: pgsql-hackers 
On 2024-Mar-12, Jelte Fennema-Nio wrote:

> On Tue, 12 Mar 2024 at 10:19, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> > Here's a last one for the cfbot.
> 
> Thanks for committing the first 3 patches btw. Attached a tiny change
> to 0001, which adds "(backing struct for PGcancelConn)" to the comment
> on pg_cancel_conn.

Thanks, I included it.  I hope there were no other changes, because I
didn't verify :-) but if there were, please let me know to incorporate
them.

I made a number of other small changes, mostly to the documentation,
nothing fundamental.  (Someday we should stop using <listentry> to
document the libpq functions and use refentry's instead ... it'd be
useful to have manpages for these functions.)

One thing I don't like very much is release_conn_addrinfo(), which is
called conditionally in two places but unconditionally in other places.
Maybe it'd make more sense to put this conditionality inside the
function itself, possibly with a "bool force" flag to suppress that in
the cases where it is not desired.

In pqConnectDBComplete, we cast the PGconn * to PGcancelConn * in order
to call PQcancelPoll, which is a bit abusive, but I don't know how to do
better.  Maybe we just accept this ... but if PQcancelStart is the only
way to have pqConnectDBStart called from a cancel connection, maybe it'd
be saner to duplicate pqConnectDBStart for cancel conns.

Thanks!

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/

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.