Merge pull request #336 from michallepicki/subquery-group-by

Use subqueries in Flop.count for queries with group_by

lib/flop.ex

@@ -779,8 +779,32 @@ defmodule Flop do
     if count = opts[:count] do
       count
     else
-      q = opts[:count_query] || q
-      apply_on_repo(:aggregate, "count", [filter(q, flop, opts), :count], opts)
+      q =
+        if opts[:count_query] do
+          filter(opts[:count_query], flop, opts)
+        else
+          q |> filter(flop, opts) |> count_query()
+        end
+
+      apply_on_repo(:aggregate, "count", [q, :count], opts)
+    end
+  end
+
+  defp count_query(query) do
+    query =
+      query
+      |> Query.exclude(:preload)
+      |> Query.exclude(:order_by)
+      |> Query.exclude(:select)
+
+    case query do
+      %{group_bys: group_bys} = query when group_bys != [] ->
+        query
+        |> Query.select(%{})
+        |> Query.subquery()
+
+      query ->
+        query
     end
   end
 

test/flop_test.exs

@@ -797,6 +797,28 @@ defmodule FlopTest do
       # custom count
       assert Flop.count(Pet, flop, count: 6) == 6
     end
+
+    test "counts entries for queries with group_by clauses" do
+      _owner_1 = insert(:owner, age: 13, pets: build_list(3, :pet))
+      _owner_2 = insert(:owner, age: 20, pets: build_list(2, :pet))
+      _owner_3 = insert(:owner, age: 22, pets: build_list(1, :pet))
+      _non_matching_owner = insert(:owner, age: 52, pets: build_list(4, :pet))
+
+      q =
+        Owner
+        |> join(:left, [o], p in assoc(o, :pets), as: :pets)
+        |> group_by([o], o.id)
+        |> select(
+          [o, pets: p],
+          %{o | pet_count: count(p.id)}
+        )
+
+      flop = %Flop{
+        filters: [%Filter{field: :age, op: :<=, value: 30}]
+      }
+
+      assert Flop.count(q, flop) == 3
+    end
   end
 
   describe "meta/3" do