Any non-toy SQL engine is going to do condition pullup and pushdown. (Well, I know at least one that only does explicit pullup, but does pushdown more implicitl

Any non-toy SQL engine is going to do condition pullup and pushdown. (Well, I know at least one that only does explicit pullup, but does pushdown more implicitly because it doesn't use a tree. The effect is largely the same, modulo some shenanigans around outer joins.) Pushdown is actually a more subtle problem than people give it credit for; it inhabits this weird space where things are too trivial to be covered in papers but is too hard to cover properly in textbooks (e.g., no coverage of multiple equalities or outer joins).