Batch loading a field in absinthe with dataloader

I have an object in my Absinthe graphql schema that looks like this:

object :match do
    field(:id, non_null(:id))
    field(:opponent, non_null(:string))
    @desc "The number of votes that have been cast so far."
    field(:vote_count, non_null(:integer), resolve: &MatchResolver.get_vote_count/2)
    # etc...
end

I’m using a resolver for vote_count that performs an ecto query using the parent match. This would run into the n+1 query problem however if a list of matches is queried. It currently looks like this:

  def get_vote_count(_root, %{source: %Match{} = match}) do
    count = match |> Ecto.assoc(:votes) |> Repo.aggregate(:count, :id)

    {:ok, count}
  end

I’m already using dataloader to batch load child entities but I’m can’t seem to get a custom run_batch function to work when using the Absinthe.Resolution.Helpers.dataloader function provided by Absinthe.

What’s the recommended approach for implementing custom batch queries using dataloader/ecto? Can someone give an example, including the schema definition part?