-- The grid serves a square medium variant between thumb and preview.
ALTER TABLE photo_objects DROP CONSTRAINT IF EXISTS photo_objects_role_check;
ALTER TABLE photo_objects ADD CONSTRAINT photo_objects_role_check
    CHECK (role IN ('original', 'thumb', 'medium', 'preview'));

-- Regenerate variants for existing photos so they gain the medium variant and a
-- square thumb. The worker rebinds roles; superseded variants are reclaimed by
-- the reference-counting collector.
INSERT INTO variant_jobs (photo_id)
SELECT id FROM photos
ON CONFLICT (photo_id) DO NOTHING;