First create a function to handle the soft delete

defmodule MyApp.Repo.Migrations.SoftDeletes do
  use Ecto.Migration

  def up do
    execute """
      CREATE FUNCTION soft_delete() RETURNS TRIGGER AS $$
        DECLARE
          command text := ' SET deleted_at = current_timestamp where id = $1';
        BEGIN
          EXECUTE 'UPDATE ' || TG_TABLE_NAME || command USING OLD.id;
          RETURN OLD;
        END;
      $$ LANGUAGE plpgsql;
    """
  end

  def down do
    execute """
      DROP FUNCTION soft_delete();
    """
  end
end

Then create the migration for you table & view

defmodule MyApp.Repo.Migrations.CreateWidgets do
  use Ecto.Migration

  def up do
    create table("all_widgets") do
      add :name, :string
      add :deleted_at, :utc_datetime
      timestamps(type: :utc_datetime)
    end

    create index("all_widgets", [:deleted_at], where: "deleted_at IS NULL", name: :widgets_deleted_at_idx)

    execute """
    CREATE VIEW widgets AS
    SELECT * FROM all_widgets WHERE deleted_at IS NULL;
    """

    execute """
    CREATE TRIGGER widgets_soft_delete_tg
    INSTEAD OF DELETE ON widgets
    FOR EACH ROW EXECUTE PROCEDURE soft_delete();
    """
  end

  def down do
    execute "DROP VIEW widgets;"
    drop table("all_widgets")
  end

end

The Ecto schema doesn't change for this. You just create a schema as you would for the widgets view. Inserts, updates, and deletes all work against the view and your Elixir code is none the wiser