Re: Prevent crash when calling pgstat functions with unregistered stats kind

On Thu, Jul 02, 2026 at 04:06:01AM +0000, Bertrand Drouvot wrote:
> I agree that the responsibility should primarily be in the extension. However,
> the issue is that the NULL dereference happens inside core code (pgstat_prep_pending_entry,
> etc.), and the resulting segfault(s) cause the postmaster to terminate all
> backends (not just the offending session).
> 
> Given that one misconfigured extension can crash all connections on the server,
> a defensive check in core seems reasonable (kind of similar to 341e9a05e7b).

Nope, this was a different thing, doable in a couple of steps:
- Load the library.
- Write custom stats.
- Stop the server, flush the stats.
- Edit the configuration, not loading the library.
- Restart the server, loading failed.

The problem of this thread ought to be blocked at its source, in the
extension itself: let's not give free hands to an extension to do what
it should not be allowed to do.  There is a similar defense in
test_custom_rmgrs, as one example.  We should just map to that.
--
Michael