groups-rank.ex

def list_groups(region \\ nil, search \\ nil) do
  query =
    from(g in Group)
    |> filter_region(region)
    |> add_rank(region)

  query |> Repo.all()
end

# When no region is past we don't need to partition, we have global rank
defp add_rank(query, nil) do
  from(g in query,
    windows: [p: [partition_by: nil, order_by: [desc: g.score]]],
    select_merge: %{group_rank: row_number() |> over(:p)}
  )
end

# When a region is passed we should partition by the region to establish a rank in each region
defp add_rank(query, _region) do
  from(g in query,
    windows: [p: [partition_by: g.region, order_by: [desc: g.score]]],
    select_merge: %{group_rank: row_number() |> over(:p)}
  )
end