refactor(optimizer): use getters to access plan base, with runtime convention checking #12980

3 / 4 tasks completed

1 task still to be completed

Task	Status
src/frontend/src/optimizer/plan_node/mod.rs	Incomplete
src/frontend/src/optimizer/plan_node/plan_base.rs	Incomplete
src/frontend/src/optimizer/plan_node/stream.rs	Incomplete
All fields in `PlanBase` are actually copied from the `core` when constructing. Exposing the fields then the mutability may lead to inconsistency and confusion.	Incomplete
It's nonsense to access a stream-specific field on a logical plan node. Currently we always fill in a dummy value for them, which is unsound. Making fields private gives us more flexibility on the internal structure, enable us to replace the product type with the sum type.	Incomplete
By forcing to access the fields through traits, we're able to further constrain the accessing through the type system. Will explore this in the next PRs.	Incomplete
I have written necessary rustdoc comments	Completed
I have added necessary unit tests and integration tests	Completed
All checks passed in `./risedev check` (or alias, `./risedev c`)	Completed
My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)	Incomplete