for some operators on Dataset, like joinWith, one needs to use an
expression which means referring to columns by name.
how can i set the column names for a Dataset before doing a joinWith?
currently i am aware of:
df.toDF("k", "v").as[(K, V)]
but that seems inefficient/anti-pattern? i shouldn't have to go to a
DataFrame and back to set the column names?
or if this is the only way to set names, and column names really shouldn't
be used in Datasets, can i perhaps refer to the columns by their position?
thanks, koert
