Thread: BUG #16405: Exception P0004 not caught in EXCEPTION WHEN OTHERS

The following bug has been logged on the website:

Bug reference:      16405
Logged by:          Jacob Crell
Email address:      jacobcrell@gmail.com
PostgreSQL version: 10.0
Operating system:   AWS Aurora
Description:

Create below function to return assertion failue:
CREATE OR REPLACE FUNCTION assert_fail()
RETURNS void
LANGUAGE plpgsql
AS $function$
BEGIN
    ASSERT FALSE, 'Assertion Failed';
END;
$function$;

Create this function to call above function and catch error:
CREATE OR REPLACE FUNCTION catch_assert_fail()
RETURNS text
LANGUAGE plpgsql
AS $function$
BEGIN
   SELECT * FROM meta.assert_fail();
   RETURN 'Function Finished';
   EXCEPTION WHEN OTHERS THEN
        RETURN 'Hit the Other exception block';
END;
$function$;

Run below to call function
SELECT * FROM catch_assert_fail()

Excepted Behavior: P0004 exception is caught in EXCEPTION WHEN OTHERS,
function returns text 'Hit the Other exception block'.
Actual Behavior: P0004 exception is raised and remains uncaught.

PG Bug reporting form <noreply@postgresql.org> writes:
> Excepted Behavior: P0004 exception is caught in EXCEPTION WHEN OTHERS,
> function returns text 'Hit the Other exception block'.
> Actual Behavior: P0004 exception is raised and remains uncaught.

That's intentional, per the documentation [1]:

    The special condition name OTHERS matches every error type except
    QUERY_CANCELED and ASSERT_FAILURE. (It is possible, but often unwise,
    to trap those two error types by name.)

            regards, tom lane

[1] https://www.postgresql.org/docs/current/plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING