postgres_duration.exs

defmodule MyApp.Type.Duration do
  use Ecto.Type

  alias Postgrex.Interval

  defguardp is_duration(value) when is_struct(value, Duration)
  defguardp is_interval(value) when is_struct(value, Interval)

  @impl true
  def type, do: :interval

  @impl true
  def cast(value) when is_interval(value), do: {:ok, from_interval(value)}
  def cast(value) when is_duration(value), do: {:ok, value}
  def cast(_value), do: :error

  @impl true
  def load(value) when is_interval(value), do: {:ok, from_interval(value)}

  @impl true
  def dump(value) when is_duration(value), do: {:ok, to_interval(value)}
  def dump(_value), do: :error

  defp from_interval(interval) do
    Duration.new!(month: interval.months, day: interval.days, second: interval.secs, microsecond: {interval.microsecs, 6})
  end

  defp to_interval(duration) do
    milliseconds = to_timeout(duration)
    %Interval{microsecs: milliseconds * 1_000}
  end
end