Comments on Increase the 255 characters limit for references

 you don't have the document reference is the object table anymore, you have to do a join through the document id (which became an inode)

see also Document Aliases and especially:

 Having another Table for storing Document References (i.e separate them from the xwikidocs table) and having unique ids for Documents would cause performance problems with Hibernate since we would need to always have 2 queries when loading a doc: one query to find the Document id from a Document Reference and another query to load the Document from its id.