Re: storing binary data

On Mon, Oct 16, 2000 at 11:22:40PM -0400, Tom Lane wrote:
> Neil Conway <nconway@klamath.dyndns.org> writes:
> > I want to store some binary data in Postgres. The data is an
> > MD5 checksum of the user's password, in binary. It will be
> > exactly 16 bytes (since it is a one-way hash).
>
> > Can I store this safely in a CHAR column?
>
> No.  CHAR and friends assume there are no null (zero) bytes.
> In MULTIBYTE setups there are probably additional constraints.
>
> You could use bytea, but I would recommend converting the checksum
> to a hex digit string and then storing that in a char-type field.
> Hex is the usual textual representation for MD5 values, no?

It is, but (IMHO) it's a big waste of space. The actual MD5 digest is
128 bits. If stored in binary form, it's 16 bytes. If stored in hex
form (as ASCII), it's 32 characters @ 1 byte per character = 32 bytes.
In Unicode, that's 64 bytes (correct me if I'm wrong).

It's not a huge deal, but it would be nice to store this efficiently.
Is this possible?

TIA,

Neil

--
Neil Conway <neilconway@home.com>
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Being able to break into computers doesn't make you a hacker any more
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