[FLINK-28861][table][docs] Update "upgrading" documentation to includ…

[dannycranmer]

…e notice regarding the Table API operator issue

What is the purpose of the change

Update documentation to add a notice regarding the Table API operator issue in FLINK-28861

Brief change log

• Updated "upgrading" documentation

Verifying this change

• Visualised locally in IDE

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• e59859a Azure: SUCCESS

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[twalthr]

Thanks for updating this section @dannycranmer. I tried to make it a bit more precise. The old behavior was not causing issues for every user. As long as the static counter starts at 0 (stable environment), the state can still be restored. This is why the ALWAYS strategy still exists.

[twalthr]

Maybe we can use the release notes that I added in the JIRA issue (slightly adapted):

For Table API: 1.15.0 and 1.15.1 generated non-deterministic UIDs for operators that make it difficult/impossible to restore state or upgrade to next patch version. A new table.exec.uid.generation config option (with correct default behavior) disables setting a UID for new pipelines from non-compiled plans. Existing pipelines can set table.exec.uid.generation=ALWAYS if the 1.15.0/1 behavior was acceptable due to a stable environment.

I tried to be as concise and helpful as possible.

[twalthr]

Feel free to shorten it if needed for the table.

[dannycranmer]

Thanks for the suggestion. I have updated it according to your recommendation, with the addition of a link to the Jira. I do not think it needs shortening, it is not tallest cell in the table. We can always shorten it in the future when it is less relevant.

[twalthr]

Thanks for the update @dannycranmer. LGTM.