Custom functions mean no caching This only applies if you are using a sub-par database. While caching computationally heavy operations is not always a good cho

Custom functions mean no caching This only applies if you are using a sub-par database. While caching computationally heavy operations is not always a good choice (since they will need to get updated when more entries are added to the dataset), chances are you will have orders of magnitudes more lookups than writes and hence it makes sense to create a computed column and index the results (and hence cache them).