[_frkl]

I'm doing the same. It's also quite nice for de-duplication, a lot of operations on our data happen on a column basis, and we need to assemble tables that are basically the same, except for one or two computed columns. I usually store all columns in a separate file, and assemble tables on the fly, also memory-mapped. Quite happy with being able to do that. Not sure how easy that would be with parquet.