Re: [RFC] new digest datatypes, or generic fixed-len hex types?

On Monday 27 July 2009 14:50:30 Alvaro Herrera wrote:
> We've developed some code to implement fixed-length datatypes for well
> known digest function output (MD5, SHA1 and the various SHA2 types).
> These types have minimal overhead and are quite complete, including
> btree and hash opclasses.
>
> We're wondering about proposing them for inclusion in pgcrypto. I asked
> Marko Kreen but he is not sure about it; according to him it would be
> better to have general fixed-length hex types. (I guess it would be
> possible to implement the digest types as domains over those.)

I think equipping bytea with a length restriction would be a very natural,
simple, and useful addition. If we ever want to move the bytea type closer to
the SQL standard blob type, this will need to happen anyway.

The case for separate fixed-length data types seems very dubious, unless you
can show very impressive performance numbers. For one thing, they would make
the whole type system more complicated, or in the alternative, would have
little function and operator support.