Bug introduced in 10.3
I am using
JoinAcross to combine two datasets, where the key is an Integer.
L = Get["https://dl.dropboxusercontent.com/u/557392/permalink/StackExchange/mathematica/107732/L.m"]; R = Get["https://dl.dropboxusercontent.com/u/557392/permalink/StackExchange/mathematica/107732/R.m"]; JoinAcross[L, R, "A", "Inner"]
The Dataset rendition of these associations is
Though this takes a couple of seconds in KNIME and/or GNU R, it takes an hour or more in Mathematica 10.3.1 on GNU/Linux.
What can I do to speed this operation up?