Computing ORA_HASH

I wrote a short Python function to compute a hash value for a given expression. The return value of the function matches the return value of ORA_HASH on inputs I tested it with in Oracle 23c on Linux x86-64.

In its simplest form, the invocation can be as follows:

>>> ora_hash(b'test')
2662839991

SQL> select ora_hash('test');

ORA_HASH('TEST')
----------------
      2662839991

Handling non-string datatypes

In case of a non-string datatype, some conversion should be performed. ORA_HASH accepts a variety of datatypes. I use NUMBER and DATE in the examples below. The procedure is essentially the same with both datatypes: need to take the internal representation of a value in Oracle and pass it to Python. It should be possible to handle any other supported datatypes following the same procedure.

NUMBER

SQL> select ora_hash(2023);

ORA_HASH(2023)
--------------
    2671887358

SQL> select dump(2023, 16);

DUMP(2023,16)
---------------------
Typ=2 Len=3: c2,15,18

>>> ora_hash(b'\xc2\x15\x18')
2671887358

DATE

SQL> select ora_hash(to_date('2023-03-01 12:34:56', 'yyyy-mm-dd hh24:mi:ss'));

ORA_HASH(TO_DATE('2023-03-0112:34:56','YYYY-MM-DDHH24:MI:SS'))
--------------------------------------------------------------
                                                     112410422
                                                     
SQL> select dump(to_date('2023-03-01 12:34:56', 'yyyy-mm-dd hh24:mi:ss'), 16);

DUMP(TO_DATE('2023-03-0112:34:56
--------------------------------
Typ=13 Len=8: e7,7,3,1,c,22,38,0

>>> ora_hash(b'\xe7\x07\x03\x01\x0c\x22\x38\x00')
112410422

Specifying max_bucket and seed_value

These parameters are also supported.

MAX_BUCKET

SQL> select ora_hash('abracadabra', 255);

ORA_HASH('ABRACADABRA',255)
---------------------------
                         82

>>> ora_hash(b'abracadabra', 255)
82

SEED_VALUE

SQL> select ora_hash('abracadabra', power(2,32)-1, 123);

ORA_HASH('ABRACADABRA',POWER(2,32)-1,123)
-----------------------------------------
                               4012392341

>>> ora_hash(b'abracadabra', seed=123)
4012392341

MAX_BUCKET and SEED_VALUE

SQL> select ora_hash('abracadabra', 255, 123);

ORA_HASH('ABRACADABRA',255,123)
-------------------------------
                            149

>>> ora_hash(b'abracadabra', 255, 123)
149