improve numerical pagination, based on #28

lib/modules/mnesia_assistant/pagination.ex

@@ -74,27 +74,31 @@ defmodule MnesiaAssistant.Pagination do
   # [{{tab,'$1','_','_','_','_','_','_','_','_','_','_','_','_','_'},
   # [{'andalso', {'>', '$1', 20}, {'<', '$1', 30}}], ['$_']}], 11, read)
   # end).
-  def numerical(table, keys, strc, start: start, last: last) do
-    fields = {table, :"$1", :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_}
-    conds = [{eg(:and), {eg(:>), :"$1", start}, {eg(:<), :"$1", last}}]
-    spec = [{fields, conds, er(:all)}]
+  def numerical(table, keys, strc, start: start, last: last, at: at) do
+    fields =
+      ([table] ++
+         Enum.map(1..length(keys), fn x -> if(x === at, do: :"$1", else: :_) end))
+      |> List.to_tuple()
 
-    Transaction.transaction(fn -> Query.select(table, spec, :read) end)
-    |> case do
-      {:atomic, res} ->
-        tuple_to_map(res, keys, strc, [])
-
-      {:aborted, reason} ->
-        Transaction.transaction_error(reason, __MODULE__, "listing", :global, :database)
-    end
+    conds = [{eg(:and), {eg(:>=), :"$1", start}, {eg(:<=), :"$1", last}}]
+    spec = [{fields, conds, er(:all)}]
+    run_numerical_query(table, spec, keys, strc)
   end
 
-  def numerical(table, keys, strc, page, limit) when page > 0 and limit > 0 do
+  def numerical(table, keys, strc, page, limit, at) when page > 0 and limit > 0 do
     start = page * limit - limit
-    fields = {table, :"$1", :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_, :_}
-    conds = [{eg(:and), {eg(:>), :"$1", start}, {eg(:<), :"$1", page * limit}}]
+
+    fields =
+      ([table] ++
+         Enum.map(1..length(keys), fn x -> if(x === at, do: :"$1", else: :_) end))
+      |> List.to_tuple()
+
+    conds = [{eg(:and), {eg(:>), :"$1", start}, {eg(:<=), :"$1", page * limit}}]
     spec = [{fields, conds, er(:all)}]
+    run_numerical_query(table, spec, keys, strc)
+  end
 
+  defp run_numerical_query(table, spec, keys, strc) do
     Transaction.transaction(fn -> Query.select(table, spec, :read) end)
     |> case do
       {:atomic, res} ->