RLS.sql

CREATE OR REPLACE FUNCTION set_foo(foo_val varchar) RETURNS void AS $$
BEGIN
  EXECUTE format('SET SESSION my.foo TO %I', foo_val) ;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION get_foo() RETURNS varchar AS $$
DECLARE
  foo_val varchar;
BEGIN
  SHOW my.foo INTO foo_val;
  RETURN foo_val;
END;
$$ LANGUAGE plpgsql;

CREATE POLICY account_managers on accounts USING ( manager = get_foo());

DEMO:

luben=> SELECT set_foo('bar');
 set_foo 
---------
 
(1 row)

luben=> SELECT * FROM accounts ;
 manager | company | contact_email 
---------+---------+---------------
(0 rows)

luben=> SELECT set_foo('foo');
 set_foo 
---------
 
(1 row)

luben=> SELECT * FROM accounts ;
 manager | company | contact_email 
---------+---------+---------------
 foo     | co      | foo@bar.co