SparkSQL doesn't seem to like "$"'s in column names

[Corey Nolet]

I don't remember Oracle ever enforcing that I couldn't include a $ in a
column name, but I also don't thinking I've ever tried.

When using sqlContext.sql(...), I have a "SELECT * from myTable WHERE
locations_$homeAddress = '123 Elm St'"

It's telling me $ is invalid. Is this a bug?