migration to repair duplicate discussions

refs #5078

Change-Id: I12d0a952d860cacb81d2f4c4c0b2c40dc67d2af6
Reviewed-on: https://gerrit.instructure.com/5023
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Zach Wily <zach@instructure.com>

db/migrate/20110809193507_fix_duplicate_discussions.rb

@@ -0,0 +1,26 @@
+class FixDuplicateDiscussions < ActiveRecord::Migration
+  def self.up
+    DiscussionTopic.transaction do
+      duplicate_topics = DiscussionTopic.find(:all,
+        :select => 'old_assignment_id, context_id, context_type',
+        :conditions => "old_assignment_id IS NOT NULL AND workflow_state <> 'deleted' AND root_topic_id IS NULL AND context_type='Course'",
+        :group => 'old_assignment_id, context_id, context_type HAVING count(*) > 1')
+
+      duplicate_topics.each do |topic|
+        duplicates = DiscussionTopic.find(:all,
+          :conditions => ["context_id=? and context_type=? and old_assignment_id=? and workflow_state<>'deleted' and root_topic_id is null",
+                          topic.context_id, topic.context_type, topic.old_assignment_id],
+          :order => 'updated_at DESC')
+        to_keep = duplicates.shift
+        duplicate_ids = duplicates.map(&:id)
+
+        DiscussionEntry.update_all("discussion_topic_id=#{to_keep.id}", :discussion_topic_id => duplicate_ids)
+        DiscussionTopic.update_all("root_topic_id=#{to_keep.id}", :root_topic_id => duplicate_ids)
+        DiscussionTopic.delete(duplicate_ids)
+      end
+    end
+  end
+
+  def self.down
+  end
+end