On 25.07.22 14:04, Japin Li wrote:
> Yeah, they do not have unique keys, however, here we check primary keys. So,
> IMO, the description exceptions should say they do not have primary keys,
> rather than do not have unique keys.
The context of that check is that for each system catalog we pick one of
the available unique keys and designate it as the one primary key. If a
system catalog doesn't have a unique key to choose from, then we can't
do that, hence the comment. Changing the comment as suggested would
essentially be saying, this catalog has no primary key because it has no
primary key, which wouldn't be helpful.