Exception handling postgresql - postgresql

Question

Hello fellow programmers,
I have a question regarding exception handling.
I have created a function for inserting values into a table with the columns email and username with a max character length of 16 for the email and 32 for the password.
Now I want to give out an error message like 'Password too long,16 Chars max', whenever the inserted email is longer than 16 Chars.
I tried it already with the 'Name_too_long' error code.
How could I do that wiht exceptions in Postgres 10.5 ?
Thanks in advance.
EDIT: CODE that is semi functional
CREATE OR REPLACE FUNCTION users_insert(_email character varying,_passwort character varying) RETURNS void
AS $BODY$
BEGIN
INSERT INTO users(email,passwort,lastlogin)
VALUES(_email,_passwort,CURRENT_TIMESTAMP);
EXCEPTION
WHEN string_data_right_truncation
THEN RAISE NOTICE 'ERROR: INSERT TOO LONG';
END;
$BODY$
LANGUAGE plpgsql ;
EDIT: Working Code, with 2 different error messages, for each error:
CREATE OR REPLACE FUNCTION public.users_insert(
_email character varying,
_passwort character varying)
RETURNS void
LANGUAGE 'plpgsql'
COST 100
VOLATILE
AS $BODY$
BEGIN
IF LENGTH(_passwort) > 16
THEN RAISE EXCEPTION USING errcode = 50001;
END IF;
IF LENGTH(_email) > 32
THEN RAISE EXCEPTION USING errcode = 22001;
END IF;
INSERT INTO users(email,passwort,lastlogin)
VALUES(_email,_passwort,CURRENT_TIMESTAMP);
EXCEPTION
WHEN SQLSTATE '50001' THEN
RAISE NOTICE 'Password too long, 16 Chars max';
WHEN SQLSTATE '22001' THEN
RAISE NOTICE 'Email too long, 32 Chars max';
END;
$BODY$;
ALTER FUNCTION public.users_insert(character varying, character varying)
OWNER TO postgres;

Answer 1

Use an IF condition to check for lengths of specific columns and raise/handle relevant exceptions.
CREATE OR REPLACE FUNCTION users_insert(_email character varying,
_passwort character varying )
RETURNS void
AS $BODY$
BEGIN
IF LENGTH(_passwort) > 16
THEN RAISE EXCEPTION USING errcode = 50001;
END IF;
INSERT INTO users(email,passwort,lastlogin)
VALUES(_email,_passwort,CURRENT_TIMESTAMP);
EXCEPTION
WHEN SQLSTATE '50001' THEN
RAISE NOTICE 'Password too long,16 Chars max';
WHEN OTHERS THEN
raise notice '% %', SQLERRM, SQLSTATE;
END;
$BODY$
LANGUAGE plpgsql ;
Testing
knayak$# PERFORM users_insert('username2251621819101010#mail.com','password123passwod');
knayak$#
knayak$# END $$;
NOTICE: Password too long,16 Chars max
DO
knayak=# DO $$
knayak$# BEGIN
knayak$#
knayak$# PERFORM users_insert('username2251621819101010#mail.com','password');
knayak$#
knayak$# END $$;
NOTICE: value too long for type character varying(30) 22001
DO