I'm using a bytea type in PostgreSQL, which, to my understanding, contains just a series of bytes. However, I can't get it to play well with nulls. For example:

=# select length(E'aa\x00aa'::bytea);
 length
--------
      2
(1 row)

I was expecting 5. Also:

=# select md5(E'aa\x00aa'::bytea);
               md5
----------------------------------
 4124bc0a9335c27f086f24ba207a4912
(1 row)

That's the MD5 of "aa", not "aa\x00aa". Clearly, I'm Doing It Wrong, but I don't know what I'm doing wrong. I'm also on an older version of Postgres (8.1.11) for reasons outside of my control. (I'll see if this behaves the same on the latest Postgres as soon as I get home...)