Rename vars very slow

[timcadman]

This is still very slow. I think it is to do with removing the old variables and creating a new dataframe - you can see that it is performing operations on all variables in dataframe. Perhaps I could use ds.merge somehow - maybe quicker?

[davraam]

Hi Tim, It would be better if we write a client-server pair of functions for the dsBaseClient/dsBase package that will just do the renaming of column names in dataframes directly on the server-side. such function will be much quicker. What do you think?