matriv edited a comment on pull request #18479:
URL: https://github.com/apache/flink/pull/18479#issuecomment-1021436854


   > I have one specific comment about the `context` field. Why have you opted 
for mixing together in the serialization the instance identifier and the type 
identifier (composed by name and version)? For me "type" identity and 
"instance" identity are very different concepts, and they definitely deserve 
different fields.
   
   Because, with the upgrade story, we can have an `@ExecNodeMetadata` 
annotation with the same name, on a subclass of a current ExecNode class, which 
does something new/different and defines a newer `version`. So we need the 
combination of `name` + `version` to uniquely identify the class when we lookup 
and rebuild the Java object graph from the JSON plan.
   
   ```
   @ExecNodeMetadata(name="myNode", version=1)
   public class MyNode {}
   
   @ExecNodeMetadata(name="myNode", version=2)
   public class MyNodeWithNewFunctionality extends MyNode {}
   ```


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