Add LIMIT to total_count query when max_pages is present

closes #981

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

@@ -29,6 +29,9 @@ module Kaminari
       c = except(:offset, :limit, :order)
       # Remove includes only if they are irrelevant
       c = c.except(:includes) unless references_eager_loaded_tables?
+
+      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

kaminari-core/test/helpers/action_view_extension_test.rb

@@ -274,7 +274,7 @@ if defined?(::Rails::Railtie) && defined?(::ActionView)
                 User.max_pages 4
                 users = User.page(4).per(10)
 
-                assert_equal 'Displaying users <b>31&nbsp;-&nbsp;40</b> of <b>50</b> in total', view.page_entries_info(users)
+                assert_equal 'Displaying users <b>31&nbsp;-&nbsp;40</b> of <b>40</b> in total', view.page_entries_info(users)
               ensure
                 User.max_pages nil
               end
@@ -344,9 +344,8 @@ if defined?(::Rails::Railtie) && defined?(::ActionView)
             end
 
             test 'the last page with default entry name' do
-              User.max_pages 4
-              users = User.page(4).per(10)
-              assert_equal 'Displaying Benutzer <b>31&nbsp;-&nbsp;40</b> of <b>50</b> in total', view.page_entries_info(users,  entry_name: 'Benutzer')
+              users = User.page(5).per(10)
+              assert_equal 'Displaying Benutzer <b>41&nbsp;-&nbsp;50</b> of <b>50</b> in total', view.page_entries_info(users,  entry_name: 'Benutzer')
             end
           end
         end
@@ -393,9 +392,8 @@ if defined?(::Rails::Railtie) && defined?(::ActionView)
           end
 
           test 'the last page with default entry name' do
-            User.max_pages 4
-            users = User.page(4).per(10)
-            assert_equal 'Displaying utilisateurs <b>31&nbsp;-&nbsp;40</b> of <b>50</b> in total', view.page_entries_info(users,  entry_name: 'utilisateur')
+            users = User.page(5).per(10)
+            assert_equal 'Displaying utilisateurs <b>41&nbsp;-&nbsp;50</b> of <b>50</b> in total', view.page_entries_info(users,  entry_name: 'utilisateur')
           end
         end
       end

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

@@ -99,6 +99,33 @@ if defined? ActiveRecord
       test 'calculating total_count with GROUP BY ... HAVING clause' do
         assert_equal 2, Authorship.group(:user_id).having("COUNT(book_id) >= 3").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|
+            assert_not_match /LIMIT/, payload[:sql]
+          end
+
+          assert_equal 7, User.page.total_count
+        ensure
+          ActiveSupport::Notifications.unsubscribe subscriber
+        end
+      end
+
+      test 'total_count with max_pages adds "LIMIT (max_pages * per_page)" to the count query' do
+        begin
+          subscriber = ActiveSupport::Notifications.subscribe 'sql.active_record' do |_, __, ___, ____, payload|
+            assert_match /LIMIT/, payload[:sql]
+          end
+
+          User.max_pages 10
+
+          assert_equal 7, User.page.total_count
+        ensure
+          User.max_pages nil
+          ActiveSupport::Notifications.unsubscribe subscriber
+        end
+      end
     end
   end
 end