Ecto queries are a DSL to build sql queries, which you can see when doing e.g. Repo.to_sql(:all, query). It therefore cannot allow you do run any actual elixir functions – the db wouldn’t know what to do with them. select specifically goes a bit astray from the plain sql in that it allows you to supply a non tabular format for data, which the data returned from the db is then mapped into. That still doesn’t allow you to use elixir functions though. For arbitrary transformations map the data manually after having loaded it from the db.
