ne 23. 1. 2022 v 9:10 odesílatel Julien Rouhaud <rjuju123@gmail.com> napsal:
Hi,
On Fri, Jan 21, 2022 at 09:23:34PM +0100, Pavel Stehule wrote: > > I am sending updated patches
I've been looking a bit deeper at the feature and I noticed that there's no locking involved around the session variable usage, and I don't think that's ok. AFAICS any variable used in a session will be cached in the local hash table and will never try to access some catalog or cache, so I don't have any naive scenario that would immediately crash, but this has some other implications that seems debatable.
For instance, right now nothing prevents a variable from being dropped while another session is using it.
Obviously we can't lock a session variable forever just because a session assigned a value once ages ago, especially outside of the current transaction. But if a session set a variable in the local transaction, I don't think that it's ok to have a subsequent query failing because someone else concurrently dropped the variable.
I only backlogged this current thread but I didn't see that being discussed.
Isn't there enough stability of the system cache? sinval is sent at the moment when changes in the system catalog are visible. So inside query execution I don't see that the variable was dropped in another session.
