> the cost/time of retrieving a possibly large amount of data for that computation in this case doing it in application space is really problematic because you

> the cost/time of retrieving a possibly large amount of data for that computation in this case doing it in application space is really problematic because you can't formulate the next query until you see the result of the first - so you will be iterating over and over with sequential queries in your bread or depth first search - really problematic. So while there are many things where it's neutral technically and more a matter of design aesthetic / principle where things go.... in this case it's solving something that just cannot be done sensibly in application space (at least, without large and complex caching logic ...).