Can’t edit category slug ?

I was trying to reorganize blog’s category and tag last night, but i keep getting error unable to change category slug , the error message is very general, just mention that it cannot update the category.

I search through wordpress forum and google , it seem like this is not a wordpress bug because there are not many people talking about it, just some user mention it but without any reply, after few hour play around and looking into database & code level, finally i resolve the problem.

This happen after wordpress 2.3 release and introduce tag feature , the database structure has been changed, it combine the links category, post category and tag in one table, because for category slug it need to be unique, when you unable to change means the “word” has been used either by link category or tag.

The simple solutions is use another slug or get any tag management plugin to remove the “word” that you are planning to use as your category slug, i recommend use Simple Tags to handle the tag management.

I just wonder can’t the error message more meaningful ? it just like some stupid system design “This happen because of error xxxx0xxx000″