CALCITE-2116, a RelNode will be reused based on digest, but now many nodes's digests do not have type info, e.g. LogicalProject, this will affect some rules when we wanna transform to a node with same digest and same type (HepPlanner may pick out a RelNode with different type).
So, we should add type info just like VolcanoPlanner.
We encounter this problem with plan like below:
We wanna cast a from bigint -> int so we can have a union with project1 and project3, but with ProjectMergeRule, while merging project1 and project2, HepPlanner will think project2 and project1 are identical and it gives back project2. But actually we wanna pick project1.