Length of Identity URL

[Martin Atkins]

I'm currently working on a simple OpenID consumer app as a test, and 
have as a result created a database table to retain known users and 
their profile information.

I'm allocating a 50-character VARCHAR field for storing the Identity 
URL, but it occurs to me that a URL can theoretically be of any length.

I think then that the spec should give a recommended maximum URL length 
after which consumers are allowed to reject the URL. Users who try to 
assert longer URLs must then be prepared for it to fail in some cases.

I just picked 50 arbitrarily. I welcome discussion on what a good value 
would be. Currently we've only LiveJournal's URLs to work with as an 
example, and these have a maximum length of 39 characters. The 
modestly-named GreatestJournal could theoretically push that up to 43 if 
it upgrades to support OpenID. (I'm assuming storing the URL in 
canonical form with a 15-character username)