Merge pull request rails#35850 from kamipo/fix_count_all_with_eager_loading_and_select_and_order

Fix `count(:all)` with eager loading and explicit select and order

Author: kamipo

activerecord/lib/active_record/relation/calculations.rb

@@ -129,11 +129,12 @@ def calculate(operation, column_name)
         relation = apply_join_dependency
 
         if operation.to_s.downcase == "count"
-          relation.distinct!
-          # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT
-          if (column_name == :all || column_name.nil?) && select_values.empty?
-            relation.order_values = []
+          unless distinct_value || distinct_select?(column_name || select_for_count)
+            relation.distinct!
+            relation.select_values = [ klass.primary_key || table[Arel.star] ]
           end
+          # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT
+          relation.order_values = []
         end
 
         relation.calculate(operation, column_name)

activerecord/test/cases/calculations_test.rb

@@ -243,6 +243,12 @@ def test_count_with_eager_loading_and_custom_order
     assert_queries(1) { assert_equal 11, posts.count(:all) }
   end
 
+  def test_count_with_eager_loading_and_custom_select_and_order
+    posts = Post.includes(:comments).order("comments.id").select(:type)
+    assert_queries(1) { assert_equal 11, posts.count }
+    assert_queries(1) { assert_equal 11, posts.count(:all) }
+  end
+
   def test_count_with_eager_loading_and_custom_order_and_distinct
     posts = Post.includes(:comments).order("comments.id").distinct
     assert_queries(1) { assert_equal 11, posts.count }

activerecord/test/cases/relations_test.rb

@@ -985,6 +985,12 @@ def test_size_with_eager_loading_and_custom_order
     assert_queries(1) { assert_equal 11, posts.load.size }
   end
 
+  def test_size_with_eager_loading_and_custom_select_and_order
+    posts = Post.includes(:comments).order("comments.id").select(:type)
+    assert_queries(1) { assert_equal 11, posts.size }
+    assert_queries(1) { assert_equal 11, posts.load.size }
+  end
+
   def test_size_with_eager_loading_and_custom_order_and_distinct
     posts = Post.includes(:comments).order("comments.id").distinct
     assert_queries(1) { assert_equal 11, posts.size }