Comment 3 for bug 736011

So when late evaluation of milestones is happening, something is loading *references* to milestones but not the milestones. So selection by milestone isn't necessary. The sql log is often a good hint to the cause of this sort of thing: right before the 501 milestones start we have
7. 51 61ms SQL-launchpad-main-slave
SELECT ProductRelease.changelog,
       ProductRelease.datecreated,
       ProductRelease.datereleased,
       ProductRelease.id,
       ProductRelease.milestone,
       ProductRelease.OWNER, ProductRelease.release_notes
FROM Milestone,
     ProductRelease
WHERE Milestone.productseries = 4155
  AND ProductRelease.milestone = Milestone.id
ORDER BY datereleased DESC

which is grabbing all the releases of productseries 'main' for libpng: 777 rows.

My guess is that the traversal is being done via looking in a python property rather than a direct lookup for the specific release.