I am working on the library that will allow something like:

defmodule Foo do
  defq rating(rating) do
    case rating do
      "G" -> "General Audiences", 
      "R" -> "Restricted", 
      "PG" -> "Parental Guidance"
    end
  end

  def query do
    from m in Foo,
      select: rating(m.rating)
  end
end

But it staled a little since I do not have enough time to spare. But the above example should work more or less.

Personally I favor terseness in my Ecto queries so I would prefer a syntax more like this:

case(m.rating, %{
  "G" => "General Audiences", 
  "R" => "Restricted", 
  "PG" => "Parental Guidance"}, m.rating)

Also, FWIW I’ve yet to find a case when I’ve needed case despite maintaining a fairly extensive reporting system. I’d be tempted to say it’s almost a code smell in Ecto. For example, this example looks like it’s formatting the data, logic I prefer to keep in views. The other place I’ve seen it is in totaling with conditions which, at least in PSQL, can be converted to filter.

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