Cache replace strategy

[windscope]

1
For this dilemma:

1. if we cache table a, table b, table a.join.b
2. a and b are much less than the a.join.b, what cache replacement strategy is going to take?

2
For this dilemma:

1. cache table a.join.b, table a and table b are in disk
2. table a and table b can be filtered a lot from the predicate. a.join.b is very large
   Choose which?

A solution for both of these dilemma is a sophisticated cost estimator.