Qual é o algoritmo usado pela função ORA_HASH?

select avg(ora_hash(rownum)) id from
(select rownum from dual connect by rownum <= 1e4),
(select rownum from dual connect by rownum <= 1e4);

• 
  Se você estiver no Windows, poderá usar o ostackprof do TANEL PODER ( https://blog.tanelpoder.com/2008/10/31/advanced-oracle-troubleshooting-guide-part-9-process-stack -profiling-from-sqlplus-using-ostackprof/ )
  
• 
  Se você estiver no *nix, poderá usar o dtrace(http://www.oracle.com/technetwork/articles/servers-storage-dev/dtrace-on-linux-1956556.html ), Flame Graph (cenário de uso https://blog.dbi -services.com/oracle-database-multilingual-engine-mle/ )
  

extern "C" ub4 hash( ub1 *k, ub4 length, ub4 initval)

SQL> select ora_hash(utl_raw.cast_to_raw('0'), power(2, 32) - 1, 0) oh1,
  2         ora_hash('0', power(2, 32) - 1, 0) oh2,
  3         ora_hash(0, power(2, 32) - 1, 0) oh3,
  4         ora_hash(chr(0), power(2, 32) - 1, 0) oh4
  5    from dual;

       OH1        OH2        OH3        OH4
---------- ---------- ---------- ----------
3517341953 3517341953 1475158189 4056412421

int main()
{
    ub1 ta[] = {0};
    ub1* t = ta;
    cout << hash(t, 1, 0) << endl;
    ub1 ta0[] = {'0'};
    ub1* t0 = ta0;
    cout << hash(t0, 1, 0) << endl;
    return 0;
}

1843378377
4052366646

SQL> select dbms_utility.get_hash_value('0', 0 + 1, 1e6 + 1) ha1,
  2         ora_hash('0', 1e6, 0) + 1 ha2
  3    from dual;

       HA1        HA2
---------- ----------
    338437     338437

  function get_hash_value(name varchar2, base number, hash_size number)
    return number is
  begin
    return(icd_hash(name, base, hash_size));
  end;

  function icd_hash(name      varchar2,
                    base      binary_integer,
                    hash_size binary_integer) return binary_integer;
  pragma interface(c, icd_hash);