Description of problem:
Configure -> Smart class parameters page may take long time to load when they are hundreds of puppet environments and puppet classes.

The issue appears to be the "eager_load" joins which may be very expensive when there are too many rows. When I try to use "includes" instead of eager_load, the page load many times faster. Previously it spent 170+ seconds to load the page, now only ~5seconds or less.


# diff -u /tmp/puppetclass_lookup_keys_controller.rb.orig /usr/share/foreman/app/controllers/puppetclass_lookup_keys_controller.rb 
--- /tmp/puppetclass_lookup_keys_controller.rb.orig	2018-10-29 18:06:04.103966839 +1000
+++ /usr/share/foreman/app/controllers/puppetclass_lookup_keys_controller.rb	2018-10-29 18:08:03.990375270 +1000
@@ -4,7 +4,7 @@
   before_action :setup_search_options, :only => :index
 
   def index
-    @lookup_keys = resource_base_search_and_page(:param_classes).smart_class_parameters
+    @lookup_keys = resource_base_search_and_page.includes(:param_classes).distinct.smart_class_parameters
     @puppetclass_authorizer = Authorizer.new(User.current, :collection => @lookup_keys.map{|key| key.param_class.try(:id)}.compact.uniq)
   end