RenameFields allows specific fields in a schema to be renamed. The field values in input rows are left unchanged, only the schema is modified. This transform is often used to prepare records for output to a schema-aware sink, such as an RDBMS, to make sure that the PCollection schema field names match that of the output. It can also be used to rename fields generated by other transforms to make them more usable (similar to SELECT AS in SQL). Nested fields can also be renamed using the field-selection syntax.
input.apply(RenameFields.<PurchasePojo>create()
.rename("userId", "userIdentifier")
.rename("shippingAddress.streetAddress", "shippingAddress.street"));
Results in the same set of unmodified input elements, however the schema on the PCollection has been changed to rename userId to userIdentifier and shippingAddress.streetAddress to shippingAddress.street.
In the playground window you can find examples of using the Rename. By running this example, you will see user statistics in certain games. Since you specified in the score scheme as equal to the field with userId, it can be changed directly:
.apply(RenameFields.create()
.rename("userId", "id")
.rename("userName", "name")
.rename("score","point"));