HarlanH/DataFrames.jl — pull request #226 by kmsquire (2013-04-01 23:11:39+00:00)
Title: Bugfix: fix overflow in groupby

When grouping by multiple columns in a large-ish `DataFrame`,
the `Uint16` sort value has the potential to overflow if there
are a large number of categories. This forces it to be a
`Uint64`.