Chris, thanks for taking a stab, but I'm still looking for a more detailed cause->effect.
Hi there. In my experience, you'll run into a couple of issues:
1) How do you guarantee the string is unique? I'm guessing that you
need to create a random string, validate that it is not already
existent in the database, then recreate it until you find a unique
key. This is slower than numeric auto incrementing keys
2) Storage of numeric keys is faster and smaller than alphanumerics
I've worked with alphanum keys for many years across many apps, so I've been through all the above types of debates. These are reasons why some people prefer numerics, but they're not reasons why alphanumerics won't work in Rails.
3) Rails is built around numeric primary keys. This might not matter
in your case since you are using a legacy database, but with a new
pure Rails db, its better to follow the conventions.
Not trying to be a dweeb, but this is the type of statement I keep seeing. There's no technical facts in there which identifies the conditions under which a non-numeric key will cause Rails to cough up a lung.
Convention is one thing, but where will Rails actually break if it is not followed?