[FLINK-21710][table-planner-blink] FlinkRelMdUniqueKeys gets incorrect result on TableScan after project push-down

[godfreyhe]

What is the purpose of the change

FlinkRelMdUniqueKeys#getTableUniqueKeys uses the original columns to find the index of primary keys. But after project push-down, the indexes is incorrect based on original columns, and the new columns should be used. This pr aims to fix it.

Brief change log

• FlinkRelMdUniqueKeys gets incorrect result on TableScan after project push-down
• Clean the unused code in FlinkRelMdUniqueKeys

Verifying this change

This change added tests and can be verified as follows:

• Extended FlinkRelMdUniqueKeysTest to verify the change

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

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

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Last check on commit caf54ac (Wed Mar 10 09:53:35 UTC 2021)

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[lincoln-lil]

LGTM!

[godfreyhe]

Thanks for the review @lincoln-lil , I will merge this pr