Best type to use for enum-like behavior

[Jon Drukman]

I am going to store two totally different types of documents in a single 
solr instance.  Eventually I may separate them into separate instances 
but we are a long way from having either the size or traffic to require 
that.

I read somewhere that a good approach is to add a 'type' field to the 
data and then use a filter query.  What data type would you use for the 
type field?  I could just an integer but then we have to remember that 
1=user, 2=item, and so on.  In mysql there's an enum type where you use 
text labels that are mapped to integers behind the scenes (good 
performance and user friendly).  Is there something similar in solr or 
should I just use a string?

-jsd-