Handle duplicate column names in Table.Reader implementation (#666)

lib/postgrex/result.ex

@@ -32,7 +32,17 @@ if Code.ensure_loaded?(Table.Reader) do
  end
 
  def init(result) do
- {:rows, %{columns: result.columns, count: result.num_rows}, result.rows}
+ {columns, _} =
+ Enum.map_reduce(result.columns, %{}, fn column, counts ->
+ counts = Map.update(counts, column, 1, &(&1 + 1))
+
+ case counts[column] do
+ 1 -> {column, counts}
+ n -> {"#{column}_#{n}", counts}
+ end
+ end)
+
+ {:rows, %{columns: columns, count: result.num_rows}, result.rows}
  end
  end
 end

test/query_test.exs

@@ -1715,19 +1715,20 @@ defmodule QueryTest do
  assert {:ok, res} =
  P.query(
  context[:pid],
- "SELECT * FROM (VALUES (1, 'a'), (2, 'b'), (3, 'c')) AS tab (x, y)",
+ "SELECT *, 1 AS x FROM (VALUES (1, 'a'), (2, 'b'), (3, 'c')) AS tab (x, y)",
  []
  )
 
  assert res |> Table.to_rows() |> Enum.to_list() == [
- %{"x" => 1, "y" => "a"},
- %{"x" => 2, "y" => "b"},
- %{"x" => 3, "y" => "c"}
+ %{"x" => 1, "y" => "a", "x_2" => 1},
+ %{"x" => 2, "y" => "b", "x_2" => 1},
+ %{"x" => 3, "y" => "c", "x_2" => 1}
  ]
 
  columns = Table.to_columns(res)
  assert Enum.to_list(columns["x"]) == [1, 2, 3]
  assert Enum.to_list(columns["y"]) == ["a", "b", "c"]
+ assert Enum.to_list(columns["x_2"]) == [1, 1, 1]
 
  assert {_, %{count: 3}, _} = Table.Reader.init(res)
  end