Comment 3 for bug 301187

I will have to check the query itself to to see if it's a select count() and act accordingly, otherwise a legitimate query that returns no rows may provide a surprising result (not an empty batch).

Borrowing behaviour from apex, the count() query should return just the integer. It's a different enough kind of query to warrant this, and since SOQL isn't SQL, I don't feel quite so bad about the different behaviour.