Add migration with extension column to uploads.

db/migrate/20170609115401_add_extension_to_topic_links.rb

@@ -1,6 +1,6 @@
 class AddExtensionToTopicLinks < ActiveRecord::Migration
   def change
-    add_column :topic_links, :extension, :string, limit: 5
+    add_column :topic_links, :extension, :string, limit: 10
     add_index :topic_links, :extension
   end
 end

db/migrate/20170703115216_add_extension_to_uploads.rb

@@ -0,0 +1,11 @@
+class AddExtensionToUploads < ActiveRecord::Migration
+  def up
+    add_column :uploads, :extension, :string, limit: 10
+    execute "CREATE INDEX index_uploads_on_extension ON uploads(lower(extension))"
+  end
+
+  def down
+    remove_column :uploads, :extension
+    execute "DROP INDEX index_uploads_on_extension"
+  end
+end