Julia performs poorly on group-by benchmarks

[Juan]

The benchmarks could be redone with the new dataframes v0.15.

Release announcements for DataFrames.jl

I think categorical arrays are not optimized for only 100 observations per group. The typical ratio would be much higher than that. Do you get the same result with 1000 or 10000?

Release notes for the DataFrames.jl package v0.15.0

Another good options is

GitHub - JuliaString/InternedStrings.jl: Fully transparent string interning...