Elixir vs Rust: delete all ?ei= or &ei= from URL

sanitize.ex

  defp sanitize_url(s) do
    uri       = URI.parse(s)
    new_query = case uri.query do
      nil   -> nil
      query ->
        query
        |> URI.decode_query()
        |> Map.delete("ei")
        |> URI.encode_query()
    end
    new_uri = %{uri | query: new_query}
    URI.to_string(new_uri)
  end

sanitize.rs

fn set_query_pairs(url: &mut Url, pairs: Vec<(String, String)>) {
    let mut query_pairs = url.query_pairs_mut();
    query_pairs.clear();
    for (k, v) in pairs.iter() {
        query_pairs.append_pair(k, v);
    }
}

pub(crate) fn sanitize_url(url: &str) -> String {
    let mut url = Url::parse(url).unwrap();
    let wanted_pairs =
        url.query_pairs()
            .filter_map(|(k, v)| {
                match k {
                    Cow::Borrowed("ei") => None,
                    _ => Some((k.to_string(), v.to_string()))
                }
            })
            .collect::<Vec<_>>();
    set_query_pairs(&mut url, wanted_pairs);
    url.to_string()
}

The Rust version is split up into two functions to avoid a silly drop(query_pairs)

Elixir disadvantages: it can't process more than one of the same query key:

iex(5)> URI.decode_query("a=3&a=4")
%{"a" => "4"}