How do I set a maximum length (in characters) of a CLOB field

Question

Hi,
I've seen some questions like this around, but I did not find a clear answer.
This is my problem: I want to make my CLOB field to accept a maximum of 32768 characters. This is because I need other data manipulation tools to receive an ORA error when they try to insert or update text larger than 32768.
I tried with an Insert/Update trigger, but I received ORA error that actually means that LOB fields can not be used in update trigger(or something).
Please, help!

Answer 1

Maybe, Not a neat way to do things, but seems to work.
Others may be able to suggest better solutions.
SQL> create table test_lob(lob clob) ;
Table created.
SQL> CREATE OR REPLACE FUNCTION getlength(p_lob CLOB) RETURN NUMBER DETERMINISTIC IS
  2  BEGIN
  3      IF (dbms_lob.getlength(p_lob) > 32768)
  4      THEN
  5          raise_application_error(-20100,
  6                                  'Text may not be greater than 32768 characters!');
  7      ELSE
  8          RETURN NULL;
  9      END IF;
10  END;
11  /
Function created.
SQL> create index idx_test_lob on test_lob(getlength(lob)) ;
Index created.
SQL>
SQL> declare
  2    l_lob CLOB ;
  3  begin
  4    insert into test_lob values (empty_clob()) returning lob into l_lob ;
  5    dbms_lob.writeappend(l_lob, 32767, rpad('*', 32767, '*')) ;
  6  end ;
  7  /
PL/SQL procedure successfully completed.
SQL> declare
  2    l_lob CLOB ;
  3  begin
  4    insert into test_lob values (empty_clob()) returning lob into l_lob ;
  5    dbms_lob.writeappend(l_lob, 32760, rpad('*', 32760, '*')) ;
  6    dbms_lob.writeappend(l_lob, 8, rpad('*', 8, '*')) ;
  7  end ;
  8  /
PL/SQL procedure successfully completed.
SQL> declare
  2    l_lob CLOB ;
  3  begin
  4    insert into test_lob values (empty_clob()) returning lob into l_lob ;
  5    dbms_lob.writeappend(l_lob, 32760, rpad('*', 32760, '*')) ;
  6    dbms_lob.writeappend(l_lob, 9, rpad('*', 9, '*')) ;
  7  end ;
  8  /
declare
ERROR at line 1:
ORA-20100:
ORA-06512: at "SYS.DBMS_LOB", line 789
ORA-06512: at line 6
SQL> select count(*) from test_lob ;
  COUNT(*)
         2
1 row selected.
SQL>