--
-- Error handling: how Ruby failures surface as PostgreSQL errors, and how
-- user code can catch and recover from them.
--
-- An uncaught RuntimeError becomes a PostgreSQL ERROR.
CREATE FUNCTION e_raise() RETURNS int LANGUAGE plruby AS $$
    raise 'boom'
$$;
SELECT e_raise();
ERROR:  boom
CONTEXT:  PL/Ruby function "e_raise"
-- A specific exception class's message is preserved.
CREATE FUNCTION e_argerror() RETURNS int LANGUAGE plruby AS $$
    Integer('not a number')
$$;
SELECT e_argerror();
ERROR:  invalid value for Integer(): "not a number"
CONTEXT:  PL/Ruby function "e_argerror"
-- A ZeroDivisionError surfaces as an error.
CREATE FUNCTION e_divzero() RETURNS int LANGUAGE plruby AS $$
    1 / 0
$$;
SELECT e_divzero();
ERROR:  divided by 0
CONTEXT:  PL/Ruby function "e_divzero"
-- Exceptions can be rescued inside the function and turned into a value.
CREATE FUNCTION e_rescued() RETURNS text LANGUAGE plruby AS $$
    begin
        raise 'inner failure'
    rescue => ex
        "caught: #{ex.message}"
    end
$$;
SELECT e_rescued();
       e_rescued       
-----------------------
 caught: inner failure
(1 row)

-- A database error from spi_exec is catchable as a Ruby exception.
CREATE FUNCTION e_spi_caught() RETURNS text LANGUAGE plruby AS $$
    begin
        spi_exec('select * from a_table_that_does_not_exist')
        'no error'
    rescue => ex
        'caught spi error'
    end
$$;
SELECT e_spi_caught();
   e_spi_caught   
------------------
 caught spi error
(1 row)

-- Returning the wrong shape is a datatype error.
CREATE FUNCTION e_wrong_array() RETURNS int[] LANGUAGE plruby AS $$
    42
$$;
SELECT e_wrong_array();
ERROR:  function declared to return array must return an array
CONTEXT:  PL/Ruby function "e_wrong_array"
-- elog('ERROR', ...) aborts like a PostgreSQL error.
CREATE FUNCTION e_elog() RETURNS void LANGUAGE plruby AS $$
    elog('ERROR', 'explicit elog error')
$$;
SELECT e_elog();
ERROR:  explicit elog error
CONTEXT:  PL/Ruby function "e_elog"
-- After an error, the session remains usable.
CREATE FUNCTION e_ok() RETURNS int LANGUAGE plruby AS $$
    123
$$;
SELECT e_ok();
 e_ok 
------
  123
(1 row)