Adjust the permissions required for COMMENT ON ROLE.

Formerly, any member of a role could change the role's comment, as of
course could superusers; but holders of CREATEROLE privilege could not,
unless they were also members.  This led to the odd situation that a
CREATEROLE holder could create a role but then could not comment on it.
It also seems a bit dubious to let an unprivileged user change his own
comment, let alone those of group roles he belongs to.  So, change the
rule to be "you must be superuser to comment on a superuser role, or
hold CREATEROLE to comment on non-superuser roles".  This is the same
as the privilege check for creating/dropping roles, and thus fits much
better with the rule for other object types, namely that only the owner
of an object can comment on it.

In passing, clean up the documentation for COMMENT a little bit.

Per complaint from Owen Jacobson and subsequent discussion.

1 files changed, 1 insertions, 14 deletions

diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index 63f22d8adc2..f13eb2891e2 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -58,20 +58,7 @@ static void DelRoleMems(const char *rolename, Oid roleid,
 static bool
 have_createrole_privilege(void)
 {
-	bool		result = false;
-	HeapTuple	utup;
-
-	/* Superusers can always do everything */
-	if (superuser())
-		return true;
-
-	utup = SearchSysCache1(AUTHOID, ObjectIdGetDatum(GetUserId()));
-	if (HeapTupleIsValid(utup))
-	{
-		result = ((Form_pg_authid) GETSTRUCT(utup))->rolcreaterole;
-		ReleaseSysCache(utup);
-	}
-	return result;
+	return has_createrole_privilege(GetUserId());
 }