I have a byte array (16 elements in length) that identifies a JPEG image
(it's the MD5 message digest), and I'd like to store it in the DB I use
to sort my collection as the primary key so I can spot duplicates easily.

I can turn that array into a Base64 varchar or into an hexadecimal
representation but before that I want to explore other options.
I'm not completely sure if an array datatype can be part of a primary
key. Even if that is possible, is that convenient? Is it better to make
that into a varchar?

I'm sure this has been done in some problem domains that deal a lot with
arrays and with numbers in general.

Thank you!