Helper class to manage snapshots and deltas and keep not only a contiguous JS array of data per column in the
underlying table, but also support a mapping function to let client code translate data in some way for display and
keep that cached as well.
Removes some column from the cache, avoiding extra computation on incoming events, and possibly freeing some
memory. If this pair of column name and map function are requested again, it will be recomputed from scratch.
Helper class to manage snapshots and deltas and keep not only a contiguous JS array of data per column in the underlying table, but also support a mapping function to let client code translate data in some way for display and keep that cached as well.