PERF/FIX: Dismiss Post coming back

Now that post numbers are monotonically increasing we should not need this job
Stuff should just self correct as users browser along

Corrected the job not to reset the disimissed posts in case we need it

app/jobs/scheduled/ensure_db_consistency.rb

@@ -4,7 +4,6 @@ module Jobs
     every 12.hours
 
     def execute(args)
-      TopicUser.ensure_consistency!
       UserVisit.ensure_consistency!
       Group.refresh_automatic_groups!
       Notification.ensure_consistency!

app/models/topic_user.rb

@@ -230,10 +230,15 @@ class TopicUser < ActiveRecord::Base
   end
 
   def self.ensure_consistency!(topic_id=nil)
+    # TODO this needs some reworking, when we mark stuff skipped
+    # we up these numbers so they are not in-sync
+    # the simple fix is to add a column here, but table is already quite big
+    # long term we want to split up topic_users and allow for this better
     builder = SqlBuilder.new <<SQL
+
 UPDATE topic_users t
   SET
-    last_read_post_number = last_read,
+    last_read_post_number = LEAST(GREATEST(last_read, last_read_post_number), max_post_number),
     seen_post_count = LEAST(max_post_number,GREATEST(t.seen_post_count, last_read))
 FROM (
   SELECT topic_id, user_id, MAX(post_number) last_read
@@ -251,7 +256,7 @@ SQL
 X.topic_id = t.topic_id AND
 X.user_id = t.user_id AND
 (
-  last_read_post_number <> last_read OR
+  last_read_post_number <> LEAST(GREATEST(last_read, last_read_post_number), max_post_number) OR
   seen_post_count <> LEAST(max_post_number,GREATEST(t.seen_post_count, last_read))
 )
 SQL