Re: Issues with ON CONFLICT UPDATE and REINDEX CONCURRENTLY

On Sun, Nov 23, 2025 at 01:14:37PM +0100, Alvaro Herrera wrote:
> Yes, exactly that ... but can this be used by the SQL injection points
> functionality?  The test is an isolation .spec file, and I didn't find a
> way to say "make me sleep when I hit this injection point, but only if
> conflict is false".  Or maybe I just missed it.

(Sorry for the low activity, last week was a crazy conference week and
I'm still recovering.)

Reading through v13-0001, there is currently no direct way with the
existing callbacks to do as you want, which would be to push down a
conditional wait inside the callback itself, based on a run-time
stack.  There would be two ways to do that, by extending the facility:
- Simple one: addition of a new dedicated callback, that accepts one
single boolean argument.
- More complicated one: extend the module injection_points so as it is
possible to pass down conditions that should be checked at run-time.
I've mentioned that in the past, folks felt meh.

Saying that, Mihail's patch to just run the injection point only if
conflict == false is OK, and that's what I have seen most hackers do
as a matter of simplicity.  This makes the injection point footprint
in the backend slightly larger but it's not that bad, englobed inside
an ifdef.  You could also use a secondary point for an else branch
defined in execIndexing.c, with a different name and a different
callback attached to it if you want to take a special action for the
conflict == true case.
--
Michael