Is ora_hash deterministic?

Question

I am working with an Oracle database and I need to be able to partition the data in a table. I understand that Rracle has an ora_hash function that can partition the data i

Answer 1

Jon Heller's answer has some more details, so go upvote his answer. Since this is the accepted answer still, I'll inline part of his response:

ORA_HASH is definitely deterministic for data types that can be used for partitioning, such as NUMBER, VARCHAR, DATE, etc.

But ORA_HASH is not deterministic for at least some of the other data types, such as CLOB.

Answer 2

ORA_HASH is definitely deterministic for data types that can be used for partitioning, such as NUMBER, VARCHAR, DATE, etc.

But ORA_HASH is not deterministic for at least some of the other data types, such as CLOB.

---

My answer is based on this Jonathan Lewis article about ORA_HASH.

Jonathan Lewis doesn't explicitly say they are deterministic, but he does mention that ORA_HASH "seems to be the function used internally – with a zero seed – to determine which partition a row belongs to in a hash partitioned table". And if it's used for hash partitioning then it must be deterministic, or else partition-wise joins wouldn't work.

To show that ORA_HASH can be non-deterministic for some data types, run the below query. It's from a comment in the same article:

with src as (select to_clob('42') val from dual connect by level<=5)
select val,ora_hash(val,7) from src order by 2;

Surprisingly, this same issues happens with dbms_sqlhash.gethash.