scala - How to obtain the symmetric difference between two DataFrames?

Question

In the SparkSQL 1.6 API (scala) Dataframe has functions for intersect and except, but not one for difference. Obviously, a combination of union and except can be used to generate difference:

df1.except(df2).union(df2.except(df1))

But this seems a bit awkward. In my experience, if something seems awkward, there's a better way to do it, especially in Scala.

Answer 1

You can always rewrite it as:

df1.unionAll(df2).except(df1.intersect(df2))

Seriously though this UNION, INTERSECT and EXCEPT / MINUS is pretty much a standard set of SQL combining operators. I am not aware of any system which provides XOR like operation out of the box. Most likely because it is trivial to implement using other three and there is not much to optimize there.