Github user HeartSaVioR commented on the issue:
https://github.com/apache/flink/pull/6253
If we would like to answer 1 as "Yes, apply the change to ExistingField.",
we can rebase this PR with below branch.
https://github.com/HeartSaVioR/flink/commits/FLINK-8094-fixing-ExistingField
Thanks to @xccui I can copy the test code from his POC commit in above
branch.
https://github.com/xccui/flink/commit/afcc5f1a0ad92db08294199e61be5df72c1514f8---
