Revert "Merge pull request #979 from MmKolodziej/better_total_count_for_grouped_queries"

This reverts commit b5e2e07234, reversing
changes made to d1c26fd2fc.

We merged #979 as a performance improvement, but it turns out it
introduced a couple of bugs. The solution seems to be a little tricky as
it has to call `.unscoped` and `unscope(where: :type)`, so let's revert
it until we find a better solution.

closes #1012, #1015.

kaminari-activerecord/lib/kaminari/activerecord/active_record_relation_methods.rb

@@ -32,12 +32,15 @@ module Kaminari
 
       c = c.limit(max_pages * limit_value) if max_pages && max_pages.respond_to?(:*)
 
-      # Handle grouping with a subquery
-      @total_count = if c.group_values.any?
-        c.model.from(c.except(:select).select("1")).count
-      else
-        c.count(column_name)
-      end
+      # .group returns an OrderedHash that responds to #count
+      c = c.count(column_name)
+      @total_count = if c.is_a?(Hash) || c.is_a?(ActiveSupport::OrderedHash)
+                       c.count
+                     elsif c.respond_to? :count
+                       c.count(column_name)
+                     else
+                       c
+                     end
     end
 
     # Turn this Relation to a "without count mode" Relation.

kaminari-core/test/fake_app/active_record/models.rb

@@ -26,6 +26,12 @@ class Authorship < ActiveRecord::Base
   belongs_to :user
   belongs_to :book
 end
+class CurrentAuthorship < ActiveRecord::Base
+  self.table_name = 'authorships'
+  belongs_to :user
+  belongs_to :book
+  default_scope -> { where(deleted_at: nil) }
+end
 class Readership < ActiveRecord::Base
   belongs_to :user
   belongs_to :book
@@ -43,6 +49,11 @@ end
 class User::Address < ActiveRecord::Base
   belongs_to :user
 end
+class Animal < ActiveRecord::Base; end
+class Mammal < Animal; end
+class Dog < Mammal; end
+class Cat < Mammal; end
+class Insect < Animal; end
 
 # a class that uses abstract class
 class Product < ActiveRecord::Base
@@ -63,9 +74,10 @@ class CreateAllTables < ActiveRecord::VERSION::MAJOR >= 5 ? ActiveRecord::Migrat
     create_table(:users) {|t| t.string :name; t.integer :age}
     create_table(:books) {|t| t.string :title}
     create_table(:readerships) {|t| t.integer :user_id; t.integer :book_id }
-    create_table(:authorships) {|t| t.integer :user_id; t.integer :book_id }
+    create_table(:authorships) {|t| t.integer :user_id; t.integer :book_id; t.datetime :deleted_at }
     create_table(:user_addresses) {|t| t.string :street; t.integer :user_id }
     create_table(:devices) {|t| t.string :name; t.integer :age}
+    create_table(:animals) {|t| t.string :type; t.string :name}
   end
 end
 CreateAllTables.up

kaminari-core/test/models/active_record/active_record_relation_methods_test.rb

@@ -100,6 +100,22 @@ if defined? ActiveRecord
         assert_equal 2, Authorship.group(:user_id).having("COUNT(book_id) >= 3").page(1).total_count
       end
 
+      test 'calculating total_count with GROUP BY ... HAVING clause with model that has default scope' do
+        assert_equal 2, CurrentAuthorship.group(:user_id).having("COUNT(book_id) >= 3").page(1).total_count
+      end
+
+      test 'calculating STI total_count with GROUP BY clause' do
+        {
+          'Fenton'   => Dog,
+          'Bob'      => Dog,
+          'Garfield' => Cat,
+          'Bob'      => Cat,
+          'Caine'    => Insect
+        }.each { |name, type| type.create!(name: name) }
+
+        assert_equal 3, Mammal.group(:name).page(1).total_count
+      end
+
       test 'total_count with max_pages does not add LIMIT' do
         begin
           subscriber = ActiveSupport::Notifications.subscribe 'sql.active_record' do |_, __, ___, ____, payload|