[tmarthal]

Obviously there are subtleties to things that may not be apparent, but his example makes sense to me and so does the SQL queries that are generated. The first query is operating at the "object level" and the second is operating at the "attribute level".

The first is retrieving the object and checking if it exists, and the second is just checking the parent's foreign key. Not sure that they are really the same query, if you have unenforced foreign keys.

This is not "dumb", this is analogous to checking if a pointer is null or that the contents of the pointer are null (which is a distinction that some people want to make).