Status
Current state: [Under Discussion]
Discussion thread: https://lists.apache.org/thread/dwrbsvdlkyytvsq71mmfcqbvfq5sys01
JIRA:
Released:
Motivation
As discussed above, current flink sql metadata column is fixed and cannot be compatible with metadata change of a certain connector.
DEFAULT constraint is a good way to solve this issue.
Actually the column DEFAULT is a reasonable feature and can also help in other cases (e.g. physical columns).
so we propose this flip.
Public Interfaces
DEFAULT Syntax
metadataCol
|
combine with VIRTUAL:
metadataCol_1 metadataCol_2 |
Proposed Changes
Flink Table API & SQL handles DEFAULT constraint in the ddl.
This allows user set optional default value for the columns(physical columns/metadata columns). The only difference between current column and DEFAULT column is that we have a default value on that column.
The proposed syntax also follows this concept.
Implementation
Add DEFAULT keyword like current VIRTUAL keyword. Implemented details to be added.
Compatibility, Deprecation, and Migration Plan
The DEFAULT constraint is an optional KEYWORD to let uses define default value, so we don't need to deal with migration plan. And here is no need to add deprecation.
Test Plan
Add DEFAULT constraint test cases & ensure all table & sql cases passed