FQL - Order photos in album by like_count
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I'm trying to get the photos of a Facebook album ordered by like count in FQL with a this query:

    SELECT like_info, object_id FROM photo WHERE aid="xxxxxxxxxx_xxxx" ORDER BY like_info.like_count desc

But I get an error "(#602) like_count is not a member of the like_info scalar."

    SELECT like_info, object_id FROM photo WHERE aid="xxxxxxxxxx_xxxx" ORDER BY like_info desc

does the trick, but I don't know why: isn't like_info an object? it is possible to order a query using a member of an object?