Typecase to `integer`, not `bigint` with ecto postgres

Questions & Help Questions
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Unfortunately this doesn’t quite work:

 function :int4.cast/1 is undefined (module :int4 is not available)

But this gave me an idea! I can define a custom type like this:

  defmodule Int4 do
    @behaviour Ecto.Type
    def type, do: :int4
    def cast(value), do: {:ok, value}
    def load(value), do: {:ok, value}
    def dump(value), do: {:ok, value}
  end

And now type(^value, Int4) actually does this trick!