Ora 06512/04088 triggers errors when INSERT INTO statement - regex

Question

I'm at work for a trigger which provide a "domain" for column Molteplicità in a table called Partecipa using a function.
The trigger I've created is the following:
CREATE OR REPLACE TRIGGER dominioMolteplicità
BEFORE INSERT OR UPDATE ON partecipa
FOR EACH ROW
BEGIN
IF moltepl_valido(:NEW.molteplicità) = 'f' THEN
RAISE_APPLICAZION_ERROR(-20002, 'Invalid type');
END IF;
END;
which uses the following function:
CREATE OR REPLACE FUNCTION motepl_valido(mol VARCHAR2) RETURN CHAR IS
BEGIN
IF regexp_like(LOWER(mol), ' [*]\..[*] ') THEN
RETURN 't';
ELSE
RETURN 'f';
END IF;
END;
Table Partecipa has the following columns:
CodP INT,
molteplicità VARCHAR2,
codAss INT,
className VARCHAR2,
PRIMARY KEY (codP),
FOREIGN KEY (className) REFERENCES class(name),
FOREIGN KEY (codAss) REFERENCES associazione(cod)`
and even though in my Associazione table there are rows (in particular codaAss: 42) and in my Class table there are rows (in particular className: 'Impiegato')
When I execute the following statement
insert into Partecipa(molteplicità, className, codAss)
values ('*..*', 'Impiegato', 42);
I get these errors:
ORA-20002 INVALID TYPE
ORA-06512: AT "dominioMolteplicità", line 3
ORA-04088: ERROR DURING EXECUTION OF TRIGGER "dominioMolteplicità"
(Note that if I disable my trigger, the insert statement works properly. There's some problem with the trigger, but I can't find the mistake.)

Answer 1

It's not related to the trigger.
Your function motepl_valido raises ORA-20002 INVALID TYPE if the supplied string (in this case '*..*') does not match the regex ' [*]\..[*] '. It doesn't match because it's missing the required spaces.
Demo showing the effect of a selection of regex patterns (I've added | around the patterns to show the leading and trailing spaces):
with demo (molteplicita) as
( select '*..*' from dual union all
select ' *..* ' from dual union all
select ' *x.* ' from dual )
, patterns (pattern) as
( select '[*]\..[*]' from dual union all
select ' [*]\..[*] ' from dual union all
select ' *[*]\..[*] *' from dual union all
select ' *\*\..\* *' from dual )
select '|'||pattern||'|' as pattern
, '|'||molteplicita||'|' as molteplicita
, case when regexp_like(molteplicita, pattern) then 'Yes' else 'No' end as matched
from demo cross join patterns
order by pattern, molteplicita desc;
PATTERN MOLTEPLICITA MATCHED
---------------- ------------ -------
| *[*]\..[*] *| |*..*| Yes
| *[*]\..[*] *| | *x.* | No
| *[*]\..[*] *| | *..* | Yes
| *\*\..\* *| |*..*| Yes
| *\*\..\* *| | *x.* | No
| *\*\..\* *| | *..* | Yes
| [*]\..[*] | |*..*| No
| [*]\..[*] | | *x.* | No
| [*]\..[*] | | *..* | Yes
|[*]\..[*]| |*..*| Yes
|[*]\..[*]| | *x.* | No
|[*]\..[*]| | *..* | Yes
12 rows selected.

Answer 2

Beacue your pattern doesn't conform your data
I suppose regexp_like( lower(mol), '\*..\*') would be alright, and in this case the values such as '*=-*' or '*34*' for molteplicità would work.
Btw, even using '[\*]..[\*]'(where backslash used as an escape character) as the pattern might be possible for the above regular expression.
Demo :
with t( mol ) as
(
select '*24*' from dual union all
select 'B' from dual union all
select '*=-*' from dual
)
select
case when regexp_like(lower(mol), '\*..\*') then 't' else 'f' end suggested_pattern1,
case when regexp_like(lower(mol), '[\*]..[\*]') then 't' else 'f' end suggested_pattern2,
case when regexp_like(lower(mol), '[*]\..[*]') then 't' else 'f' end original_pattern,
case when regexp_like(lower(mol), '*..*') then 't' else 'f' end anticipated_pattern
from t;
SUGGESTED_PATTERN1 SUGGESTED_PATTERN2 ORIGINAL_PATTERN ANTICIPATED_PATTERN
t t f t
f f f t
t t f t
P.S. Note that anticipated_pattern would fail also ( for mol = 'B' in the above sample).