alphagov/transition — pull request #446 by rgarner (2014-11-03 16:03:30+00:00)
Title: Add UNIQUE (site_id, path) index to mappings

* Part one of removing path_hash. See
https://www.pivotaltracker.com/story/show/74294416
* This will incur a small write performance hit when creating
large batches of mappings (unmeasured)