Replace LEFT JOIN with INNER JOIN

I see no reason why a LEFT might be needed and its the root cause of the
awful performance.

app/models/spree/order_decorator.rb

@@ -75,6 +75,12 @@ Spree::Order.class_eval do
       joins('LEFT OUTER JOIN spree_products ON (spree_products.id = spree_variants.product_id)')
   }
 
+  scope :with_line_items_variants_and_products, lambda {
+    joins('INNER JOIN spree_line_items ON (spree_line_items.order_id = spree_orders.id)').
+      joins('INNER JOIN spree_variants ON (spree_variants.id = spree_line_items.variant_id)').
+      joins('INNER JOIN spree_products ON (spree_products.id = spree_variants.product_id)')
+  }
+
   scope :not_state, lambda { |state|
     where("state != ?", state)
   }

app/services/permissions/order.rb

@@ -10,7 +10,7 @@ module Permissions
     # Find orders that the user can see
     def visible_orders
       Spree::Order.
-        with_line_items_variants_and_products_outer.
+        with_line_items_variants_and_products.
         where(visible_orders_where_values)
     end