Add consistency check to revoke duplicate badges.

app/jobs/scheduled/ensure_db_consistency.rb

@@ -9,6 +9,7 @@ module Jobs
       Group.refresh_automatic_groups!
       Notification.ensure_consistency!
       UserAction.ensure_consistency!
+      UserBadge.ensure_consistency!
     end
   end
 end

app/models/user_badge.rb

@@ -17,6 +17,17 @@ class UserBadge < ActiveRecord::Base
   after_destroy do
     Badge.decrement_counter 'grant_count', self.badge_id
   end
+
+  # Make sure we don't have duplicate badges.
+  def self.ensure_consistency!
+    dup_ids = []
+    # Single grant badges shouldn't have duplicates at all.
+    dup_ids += exec_sql("SELECT u1.id FROM user_badges u1, user_badges u2, badges WHERE u1.badge_id = badges.id AND u1.user_id = u2.user_id AND u1.badge_id = u2.badge_id AND (NOT badges.multiple_grant) AND u1.granted_at > u2.granted_at").to_a
+    # Multiple grant badges can have duplicates but not with the same post_ids.
+    dup_ids += exec_sql("SELECT u1.id FROM user_badges u1, user_badges u2, badges WHERE u1.badge_id = badges.id AND u1.user_id = u2.user_id AND u1.badge_id = u2.badge_id AND badges.multiple_grant AND u1.post_id = u2.post_id AND u1.granted_at > u2.granted_at").to_a
+    dup_ids = dup_ids.map {|x| x["id"].to_i }
+    UserBadge.where(id: dup_ids).destroy_all
+  end
 end
 
 # == Schema Information