RE: SET ROLE documentation not entirely correct

> Additionally s/INHERITS/INHERIT/

Good spot.

> The wording should be something like
>
> 8<-----------
> The specified role_name must be a role that the current session user is
> a member of directly or indirectly.
> 8<-----------

That’s certainly much better (perhaps with a comma after “of”, if I’m being pedantic).

> I believe the paragraph you cite should be reworded, but I am at a loss
> as to how best to describe the actual situation clearly. Maybe something
> like:
>
> 8<-----------
> If the session user role has the INHERIT attribute, then it
> automatically has all the privileges of every role that it is a member
> of directly, and any that it is a member of indirectly which is not
> blocked by a NOINHERIT attribute of another reachable role; in this case
> SET ROLE effectively drops all the privileges assigned directly to the
> session user and to the other roles it is a member of, leaving only the
> privileges available to the named role.
> 8<-----------
>
> Thoughts?

Again, that's much clearer than what is currently there. It might help if some of the language/definitions from pg_has_role() is used, though.

For example:
A role X is a "MEMBER" of another role Y if there is a chain of GRANTs from X to Y via zero or more intermediate roles. This allows X to execute "SET ROLE Y".
Additionally X has "USAGE" of Y if X and all the intermediate roles (but *not* necessarily Y) are marked INHERIT. In this case X automatically has the privileges of Y, without the need to "SET ROLE Y".

Just my 2p, but being fairly new to postgres' roles and privilege set-up I can tell you that the things I have found difficult, but important, to get my head around are:

* A role either pulls in all privileges it can (INHERIT) or none at all (NOINHERIT). It is not possible to create a role that all direct members are guaranteed to require, or not require, a "SET ROLE" to use (i.e. you can't mark a role as "inheritable" or "not inheritable")

* A role's attributes are not inherited by its members - SUPERUSER, CREATEROLE, etc. The CREATE ROLE docs refer to these things as both "attributes" and "privileges", which is a bit unhelpful. It would be better to refer to them only as "attributes" everywhere, so it is clear that "attributes" are never inherited whereas "privileges" can be inherited.

* As mentioned above, "X is a member of Y" implies "X can SET ROLE Y". Membership requires a GRANT chain from X to Y.

* Also mentioned above, "X has usage of Y" implies "X doesn't need to SET ROLE Y, other than to use Y's attributes". Usage requires everything apart from Y in the GRANT chain to be marked INHERIT.

Is there the ability to include diagrams or other images in the postgres docs? I think it could really help. Boxes for roles, arrows for membership - pointing from group to member (to show the flow of privileges), with a solid line if the member has INHERIT and a broken line if they have NOINHERIT... that sort of thing.

Steve.

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