Subject: pgsql: Make dblink interruptible, via new libpqsrv APIs.

From: Noah Misch <[email-masked]>
Date: Thu, 03 Apr 2025 16:36:55 +0000

Make dblink interruptible, via new libpqsrv APIs.

This replaces dblink's blocking libpq calls, allowing cancellation and
allowing DROP DATABASE (of a database not involved in the query).  Apart
from explicit dblink_cancel_query() calls, dblink still doesn't cancel
the remote side.  The replacement for the blocking calls consists of
new, general-purpose query execution wrappers in the libpqsrv facility.
Out-of-tree extensions should adopt these.

The original commit d3c5f37dd543498cc7c678815d3921823beec9e9 did not
back-patch.  Back-patch now to v16-v13, bringing coverage to all supported
versions.  This back-patch omits the orignal's refactoring in postgres_fdw.

Discussion: https://postgr.es/m/[email-masked]

Branch
------
REL_13_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/186c586c3717d050e99c14b45f8e52a5d74bc7ba

Modified Files
--------------
contrib/dblink/dblink.c                            |  25 ++--
.../libpqwalreceiver/libpqwalreceiver.c            |   9 +-
src/include/libpq/libpq-be-fe-helpers.h            | 127 +++++++++++++++++++++
3 files changed, 144 insertions(+), 17 deletions(-)