Summary of API misuses

Our static checker in powerstation finds all API misuses in source code by pattern matching and suggests a more efficient API to replace with. Common API misuse patterns are summarized in our paper. More specifically, the API misuses detected in this checker includes:

1. any?, to be replaced with (=>) exists?
2. where.first? => find_by
3. * => *.except(order)
4. each.update => update_all
5. .count => size
6. .map => .pluck
7. pluck.sum => sum
8. .pluck + pluck => SQL UNION
9. if exists? find else create end => find_or_create_by

We list how many times such misuses happen in the applications we studied, and each instance of misuse. The list can be found here.