Retrieve first_post_id manually

I had imported a phpbb forum to mybb previously. The importer script
messed up the firstpost ids. In this case most topics cannot be imported
to discourse as the script is not able to determine the topic post.

In case you are infected of this problem just uncomment this mysql
query. It will retrieve the first_post_id manually but it will slow down
the import.

script/import_scripts/mybb.rb

@@ -105,6 +105,20 @@ class ImportScripts::MyBB < ImportScripts::Base
         skip = false
         mapped = {}
 
+        # If you have imported a phpbb forum to mybb previously there might
+        # be a problem with mybb_threads.firstpost. If these ids are wrong
+        # the thread cannot be imported to discourse as the topic post is
+        # missing. This query retrieves the first_post_id manually. As it
+        # will decrease the performance it is commented out by default.
+        # m['first_post_id'] = mysql_query("
+        #   SELECT   p.pid id,
+        #   FROM     mybb_posts p,
+        #            mybb_threads t
+        #   WHERE    p.tid = #{m['topic_id']} AND t.tid = #{m['topic_id']}
+        #   ORDER BY p.dateline
+        #   LIMIT    1
+        # ").first['id']
+
         mapped[:id] = m['id']
         mapped[:user_id] = user_id_from_imported_user_id(m['user_id']) || -1
         mapped[:raw] = process_mybb_post(m['raw'], m['id'])