Merge pull request mojotech#39 from BKStephens/master

Fix total entries errors for queries with group by clause

lib/scrivener/paginater/ecto/query.ex

@@ -31,15 +31,39 @@ defimpl Scrivener.Paginater, for: Ecto.Query do
     total_entries =
       query
       |> exclude(:preload)
-      |> exclude(:select)
       |> exclude(:order_by)
+      |> prepare_select
       |> subquery
       |> select(count("*"))
       |> repo.one(caller: caller)
 
     total_entries || 0
   end
 
+  defp prepare_select(query) do
+    try do
+      query
+      |> subquery
+      |> select(count("*"))
+      |> Ecto.Query.Planner.prepare_sources(_adapter = nil)
+
+      query
+    rescue
+      e in Ecto.SubQueryError ->
+        case e do
+          %{
+            exception: %{
+              message: "subquery must select a source (t), a field (t.field) or a map" <> _rest
+            }
+          } ->
+            query
+            |> exclude(:select)
+          _ ->
+            raise e
+        end
+    end
+  end
+
   defp total_pages(0, _), do: 1
 
   defp total_pages(total_entries, page_size) do

test/scrivener/paginator/ecto/query_test.exs

@@ -205,6 +205,31 @@ defmodule Scrivener.Paginator.Ecto.QueryTest do
       assert page.total_entries == 7
     end
 
+    test "can be used with a group by clause on field other than id" do
+      create_posts()
+
+      page =
+        Post
+        |> group_by([p], p.body)
+        |> select([p], (p.body))
+        |> Scrivener.Ecto.Repo.paginate
+
+      assert page.total_entries == 7
+    end
+
+    test "can be used with a group by clause on field on joined table" do
+      create_posts()
+
+      page =
+        Post
+        |> join(:inner, [p], c in assoc(p, :comments))
+        |> group_by([p, c], c.body)
+        |> select([p, c], (c.body))
+        |> Scrivener.Ecto.Repo.paginate
+
+      assert page.total_entries == 2
+    end
+
     test "can be provided a Scrivener.Config directly" do
       posts = create_posts()