Re: multiple membership grants and information_schema.applicable_roles

Pavel Luzanov <p(dot)luzanov(at)postgrespro(dot)ru> writes:
> The application_roles view shows duplicates:

> postgres(at)postgres(17.0)=# SELECT * FROM
> information_schema.applicable_roles WHERE grantee = 'alice';
>  grantee | role_name | is_grantable
> ---------+-----------+--------------
>  alice   | bob       | NO
>  alice   | bob       | YES
> (2 rows)

AFAICT this is also possible with the SQL standard's definition
of this view, so I don't see a bug here:

CREATE RECURSIVE VIEW APPLICABLE_ROLES ( GRANTEE, ROLE_NAME, IS_GRANTABLE ) AS
( ( SELECT GRANTEE, ROLE_NAME, IS_GRANTABLE
FROM DEFINITION_SCHEMA.ROLE_AUTHORIZATION_DESCRIPTORS
WHERE ( GRANTEE IN
( CURRENT_USER, 'PUBLIC' )
OR
GRANTEE IN
( SELECT ROLE_NAME
FROM ENABLED_ROLES ) ) )
UNION
( SELECT RAD.GRANTEE, RAD.ROLE_NAME, RAD.IS_GRANTABLE
FROM DEFINITION_SCHEMA.ROLE_AUTHORIZATION_DESCRIPTORS RAD
JOIN
APPLICABLE_ROLES R
ON
RAD.GRANTEE = R.ROLE_NAME ) );

The UNION would remove rows only when they are duplicates across all
three columns.

I do see what seems like a different issue: the standard appears to expect
that indirect role grants should also be shown (via the recursive CTE),
and we are not doing that.

regards, tom lane