The following bug has been logged online:
Bug reference: 1134
Logged by: Fabien COELHO
Email address: coelho@cri.ensmp.fr
PostgreSQL version: 7.5 Dev
Operating system: any
Description: ALTER USER ... RENAME breaks md5 passwords
Details:
If you rename a user with a md5 password, the
password is broken. md5 passwords are the default,
so it means that renaming a user with a password
does not work by default.
This is because the username is used implicitly as salt. This was a bad idea
(tm).
Fixing this has implications on the client/server
protocol for md5 authentication. If you're going
to fix it some day, consider also adding more
characters to the server nonce used in the protocol.