Cost-based Rescheduling:
- Selection of runnable subtrees to execute:
- Traditional way: “maximal” one.
- Maximal efficiency: (P - MR)/(P + MW)
- MW: cost of writing materialized temporary result to disk
- MR: cost of reading temporary results form disk
- P: cost of executing the subtree
- efficiency: improvement in response time per unit of scrambling execution
- Another iteration of rescheduling is started until the delayed data has arrived.