Add map_nulls_to_nil configuration value added for converting null at…

…om in query responses to Elixir nil atom

README.md

@@ -53,6 +53,10 @@ config :my_app, MyApp.SnowflakeConnection,
     ]
 ```
 
+The odbc driver will, by default, return `:null` for empty values returned from snowflake queries.
+This will be converted to `nil` by default by Snowflex. A configuration value `map_nulls_to_nil?`
+can be set to `false` if you do not desire this behavior.
+
 Then, in your application module, you would start your connection:
 
 ```elixir

lib/snowflex.ex

@@ -75,6 +75,8 @@ defmodule Snowflex do
   end
 
   defp process_results({:selected, headers, rows}) do
+    null_to_nil? = Application.get_env(:snowflex, :map_nulls_to_nil?, true)
+
     bin_headers =
       headers
       |> Enum.map(fn header -> header |> to_string() |> String.downcase() end)
@@ -86,6 +88,7 @@ defmodule Snowflex do
           row
           |> elem(index)
           |> to_string_if_charlist()
+          |> map_null_to_nil(null_to_nil?)
 
         Map.put(map, col, data)
       end)
@@ -95,6 +98,9 @@ defmodule Snowflex do
   defp to_string_if_charlist(data) when is_list(data), do: to_string(data)
   defp to_string_if_charlist(data), do: data
 
+  defp map_null_to_nil(:null, true), do: nil
+  defp map_null_to_nil(data, _), do: data
+
   defp cast_row(row, schema) do
     schema
     |> struct()