Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> writes: > And, the /* do not unlock till end of xact */, it looks like it's been > there from day 1. It may be indicating that the ref count fo the new > relation created in heap_create_with_catalog() will be decremented at > the end of xact, but I'm not sure what it means.
Hmm, I think it's been copied-and-pasted from somewhere. It's quite common for us to not release locks on modified tables until end of transaction. However, that's not what's happening here, because we actually *don't have any such lock* at this point, as you can easily prove by stepping through this code and watching the contents of pg_locks from another session. We do acquire AccessExclusiveLock on the new table eventually, but not till control returns to DefineRelation.
I'm not real sure that I like the proposed code change: it's unclear to me whether it's an unwise piercing of a couple of abstraction layers or an okay change because those abstraction layers haven't yet been applied to the new relation at all. However, I think the existing comment is actively misleading and needs to be changed. Maybe something like
/* * Close the relcache entry, since we return only an OID not a * relcache reference. Note that we do not yet hold any lockmanager * lock on the new rel, so there's nothing to release. */ table_close(new_rel_desc, NoLock);
/* * ok, the relation has been cataloged, so close catalogs and return * the OID of the newly created relation. */ table_close(pg_class_desc, RowExclusiveLock);
+1
Personally, I prefer above code.
Given these comments, maybe changing the first call to RelationClose would be sensible, but I'm still not quite convinced.