Remove todos for deleted merge requests

db/migrate/20160331133914_remove_todos_for_deleted_merge_requests.rb

+class RemoveTodosForDeletedMergeRequests < ActiveRecord::Migration
+  def up
+    execute <<-SQL
+      DELETE FROM todos
+      WHERE todos.target_type = 'MergeRequest'
+        AND NOT EXISTS (
+              SELECT *
+              FROM merge_requests
+              WHERE merge_requests.id = todos.target_id
+                AND merge_requests.deleted_at IS NULL
+            )
+    SQL
+  end
+
+  def down
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160324020319) do
+ActiveRecord::Schema.define(version: 20160331133914) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"