As of now, we don't push the aggregates with polymorphic transition type to the data nodes. The polymorphic types are resolved at the time of execution and we create the remote query during planning. So, at planning time we do not have resolved polymorphic types. What's needed is
Either 1. a way to resolve the polymorphic types at the planner type
OR 2. a way to change the polymorphic types in tuple descriptor for the RemoteQuery plan to the resolved types at the execution time.
The later seems easier than first one.
