diff --git a/models/site.rb b/models/site.rb
index 81ff108c..d4232d72 100644
--- a/models/site.rb
+++ b/models/site.rb
@@ -200,6 +200,12 @@ class Site < Sequel::Model
 
   one_to_many :archives
 
+  def self.supporter_ids
+    parent_supporters = DB[%{SELECT id FROM sites WHERE plan_type IS NOT NULL AND plan_type != 'free'}].all.collect {|s| s[:id]}
+    child_supporters = DB[%{select a.id as id from sites a, sites b where a.parent_site_id is not null and a.parent_site_id=b.id and (a.plan_type != 'free' or b.plan_type != 'free')}].all.collect {|s| s[:id]}
+    parent_supporters + child_supporters
+  end
+
   def self.newsletter_sites
      Site.select(:email).
        exclude(email: 'nil').exclude(is_banned: true).
diff --git a/models/stat.rb b/models/stat.rb
index 83e85f9f..c50cab97 100644
--- a/models/stat.rb
+++ b/models/stat.rb
@@ -12,8 +12,9 @@ class Stat < Sequel::Model
   class << self
     def prune!
       DB[
-        "DELETE FROM stats WHERE created_at < ? AND site_id NOT IN (SELECT id FROM sites WHERE plan_type IS NOT NULL OR plan_type != 'free')",
-        (FREE_RETAINMENT_DAYS-1).days.ago.to_date.to_s
+        "DELETE FROM stats WHERE created_at < ? AND site_id NOT IN ?",
+        (FREE_RETAINMENT_DAYS-1).days.ago.to_date.to_s,
+        Site.supporter_ids
       ].first
     end