Sorry for not having paid more attention earlier, but this patch is quite broken. If it weren't misguided it'd still be wrong, because this isn't the only spot in PrepareTempTablespaces that inserts InvalidOid into the output list.
But, in fact, it's intentional that we represent the DB's default tablespace by InvalidOid in that list. Some callers of GetNextTempTableSpace need that to be the case, either for permissions-checking reasons or because they're going to store the result into a temp table's pg_class.reltablespace, where that representation is *required*.
Hmm. I guess I must've been careless in checking other callers.
I see that this is perhaps underdocumented, since while GetNextTempTableSpace's comment mentions the behavior, there's no comment about it with the data structure proper.
Yeah, it could definitely do with that. It was too many steps of indirections away to me to pick that up.
It looks to me like the actual bug here is that whoever added GetTempTablespaces() and made sharedfileset.c depend on it did not get the memo about what to do with InvalidOid. It's possible that we could safely make GetTempTablespaces() do the substitution, but that would be making fd.c assume more about the usage of GetTempTablespaces() than I think it ought to. I feel like we oughta fix sharedfileset.c, instead.
This seems to be in dc6c4c9dc2a -- adding Thomas.
A quick look -- to do things right, we will need to know the database default tablespace in this case right? Which I guess isn't there because the shared fileset isn't tied to a database. But perhaps it's as easy as something like the attached, just overwriting the oid?
