Thank you for the review!
> So, for example, if the user lacks privileges on a foreign partition,
> VACUUM/VACUUM FULL report a permission warning, whereas CLUSTER/REPACK
> report that foreign tables cannot be processed.
That was an oversight, it's fixed in v4.
> In v3, CLUSTER/REPACK warn about foreign partitions during partition
> collection, without locking them or checking privileges. OTOH,
> VACUUM/VACUUM FULL warn only after locking each partition and
> checking privileges.
The 'without locking' part seems good to me. We already have
AccessExclusiveLock on the parent, and we never actually open the
foreign partitions. And this is a preexisting repack design (checking
permissions without locking first, and then checking again after
locking, just before processing it)
