FLINK-14665, we supported computed column in planner. However, the implementation of TableSourceTable#getRowType will include computed columns which is possibly not right, because computed column is generated in the downstream Project, not in the source scan.
This is possibly lead to errors when push project into source scan which will call TableSourceTable#getRowType in the rule. Currently, all the tests are passed because we don't have a test to cover this, i.e. computed column on a projectable TableSource. We should at least add a test to cover this.