Currently, the Table & SQL API relies on Flink’s TypeInformation at different positions in the code base. The API uses it for conversion between DataSet/DataStream API, casting, and table schema representation. The planning for code generation and serialization of runtime operators.
The past has shown that TypeInformation is useful when converting between DataSet/DataStream API, however, it does not integrate nicely with SQLs type system and depends on the programming language that is used.
There is consensus to perform a big rework of the type system with a better long-term vision and closer semantics to other SQL vendors and the standard itself.
FLIP-37 discusses the mid-term and long-term plan for supported types and their semantics.