PROPOSAL - User's exception in PL/pgSQL

Hello

I did some work on implementation of user's exception. 

Generally:
o add pseudotype EXCEPTION    DECLARE excpt EXCEPTION [= 'SQLSTATE']
o change RAISE stmt
   RAISE error_level [excpt_var|sys_excpt_name] errmsg, ...
o change EXCEPTION
   EXCEPTION WHEN excpt_var|sys_excpt_name THEN ...

Rules:o User can specify SQLSTATE only from class 'U1' o Default values for SQLSTATE usr excpt are from class 'U0'o Every exception's variable has unique SQLSTATEo User's exception or system's exception can be raised only with  level EXCEPTION

Any comments, notes?

Regards
Pavel Stehule

Regres test:

create function innerfx() returns integer as $$
declare my_excpt exception = 'U0001';
begin -- using msgtext as one param of exception raise exception my_excpt '%', CURRENT_TIMESTAMP; return 1;
end $$ language plpgsql;
psql:regres.sql:6: ERROR:  Invalid class for SQLSTATE value 'U0001' for 
user's exception.
HINT:  Select any unoccupied value from class U1 which is reserved for 
user's exception.
CONTEXT:  compile of PL/pgSQL function "innerfx" near line 1
create function innerfx() returns integer as $$
declare my_excpt exception = 'U1001'; my_sec_excpt exception = 'U1001';
begin -- using msgtext as one param of exception raise exception my_excpt '%', CURRENT_TIMESTAMP; return 1;
end $$ language plpgsql;
psql:regres.sql:15: ERROR:  Invalid SQLSTATE value 'U1001' for user's 
exception.
HINT:  Select any unoccupied value from class U1 which is reserved for 
user's exception.
CONTEXT:  compile of PL/pgSQL function "innerfx" near line 3
create function innerfx() returns integer as $$
declare my_excpt exception = 'U1001';
begin -- using msgtext as one param of exception raise exception my_excpt '%', CURRENT_TIMESTAMP; return 1;
end $$ language plpgsql;
CREATE FUNCTION
create function outerfx() returns integer as $$
declare my_excpt exception = 'U1001'; alias_div_by_zero exception = 'U1002'; my_excpt_def_sqlstate exception;
begin begin   raise exception my_excpt_def_sqlstate 'foo'; exception when my_excpt_def_sqlstate then   raise notice '01 catch: %, %', sqlstate, sqlerrm; end; begin   raise notice '%', innerfx(); exception when my_excpt then   raise notice '02 catch: %, %', sqlstate, sqlerrm::timestamp; end; begin   raise exception division_by_zero 'testing'; exception when division_by_zero then   raise notice 'Divison by zero: %, %', sqlstate, sqlerrm; end; raise exception alias_div_by_zero 'Unhandled exception'; return 1;
end; $$ language plpgsql;
CREATE FUNCTION
select innerfx();
psql:regres.sql:50: ERROR:  2005-06-16 10:12:53.27408+02
DETAIL:  User's exception/notice - sqlstate: U1001, name: my_excpt
HINT:  from RAISE stmt on line 3
select outerfx();
psql:regres.sql:51: NOTICE:  01 catch: U0001, foo
psql:regres.sql:51: NOTICE:  02 catch: U1001, 2005-06-16 10:12:53.274656
psql:regres.sql:51: NOTICE:  Divison by zero: 22012, testing
psql:regres.sql:51: ERROR:  Unhandled exception
DETAIL:  User's exception/notice - sqlstate: U1002, name: 
alias_div_by_zero
HINT:  from RAISE stmt on line 21
drop function outerfx();
DROP FUNCTION
drop function innerfx();
DROP FUNCTION