Re: [HACKERS] proposal: session server side variables

 See attached scripts for instance.

Your test shows so SET SESSION has not transactional behaviour - the
transactions fails, but the value is not reverted to NULL.

There are *two* function calls, the first fails and the second succeeds. Here is the trace with a some comments:

 [...]

 ## SET SESSION x.x = 'null';
 SET
 -- previous has set x.x = 'null'

 ## SELECT setupSecurityContext(3);
 -- first setup... function call
 NOTICE:  SET secured = FALSE
 NOTICE:  SET secured = TRUE
 -- there is a SET to 'ok' just after this print
 -- at the end the transaction fails:
 ERROR:  insert or update on table "log" violates foreign key constraint "log_sid_fkey"
 DETAIL:  Key (sid)=(3) is not present in table "stuff".
 -- no result is displayed from the SELECT

 ## SHOW x.x;
 nul
 -- the value is the initial value, it has been reverted

 ## SELECT setupSecurityContext(2);
 -- second setup... function call
 NOTICE:  SET secured = FALSE
 NOTICE:  SET secured = TRUE
 -- trues is displayed, the function succeeded
  t

 ## SHOW x.x;
 ok
 -- the new value is shown

--
Fabien.