Ref. http://stackoverflow.com/questions/18969420/perform-a-semi-join-with-data-table

Matt asked for a feature request for this in the stack overflow comments; I did not see this in the issues and the feature does not appear to be implemented as of 1.9.4. I am just adding this to ensure that this is not lost, in all likelihood this is low priority.