drop table secret;
drop role alice;
drop role bob;


CREATE TABLE secret ( message text );
ALTER TABLE secret ENABLE row level security;
CREATE ROLE alice;
CREATE ROLE bob;
grant all on secret to alice;
grant all on secret to bob;

create unique index foo on secret (substring(message,'@.*?,'));
create policy p_alice on secret TO alice USING ( message like '@alice,%' ) WITH CHECK (message like '@bob,%');
create policy p_bob on secret TO bob USING ( message like '@bob,%' ) WITH CHECK (message like '@alice,%');

SET ROLE alice;
TABLE secret;

INSERT INTO SECRET VALUES ('@bob, i heard you got sick?');
INSERT INTO SECRET VALUES ('@jaque, jennifer made it onto hackers!');
INSERT INTO SECRET VALUES ('@bob, btw, heard about the dyspeptor?');
TABLE secret;

SET ROLE bob;
table secret;