Not sure if this is useful, but JuliaDB has a basic “untyped table” type ColDict. It is used to implement operation that mutate columns efficiently. A possible approach would be to load things as a ColDict and only use a fully typed version when a small subset of columns is needed for an operation (which happens with select keyword in IndexedTables or with macro magic in JuliaDBMeta).
There was even some discussion to use a DataFrame instead of ColDict (so that it would be thing that can be manipulate more easily by the user), which now that DataFrames is more lightweight, seems feasible. This would need IndexedTables to drop the “nameless table” (where columns are just numbered) and DataFrames to implement a notion of primary keys.
