[FLINK-13075][table-planner-blink] Project pushdown rule shouldn't require the TableSource return a modified schema in blink planner

[tsreaper]

What is the purpose of the change

As the javadoc of org.apache.flink.table.sources.ProjectableTableSource#projectFields said, the table schema of the TableSource copy must not be modified by this method. However, PushProjectIntoTableSourceScanRule in blink planner requires the returning a table source with the modified table schema. This conflict with the javadoc and result in the TableSource works for flink planner can't work for blink planner.

This PR fixes PushProjectIntoTableSourceScanRule and related class to make it work for blink planner.

Brief change log

• Fix PushProjectIntoTableSourceScanRule so that the schema of the newly created table source is the same with the original one.

Verifying this change

This change is already covered by existing tests, such as TableSourceItCase.

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, Yarn/Mesos, 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

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Automated Checks

Last check on commit 623248e (Tue Aug 06 15:45:15 UTC 2019)

Warnings:

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Review Progress

• ❓ 1. The [description] looks good.
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• ❓ 3. Needs [attention] from.
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• ❓ 5. Overall code [quality] is good.

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CI report:

• 8d81e84 : FAILURE Build
• 623248e : SUCCESS Build

[tsreaper]

Travis passed: https://travis-ci.com/TsReaper/flink/builds/120101168

[JingsongLi]

LGTM

[wuchong]

Can be simplified to val selectedFields: Option[Array[Int]] = None. Then we don't need to introduce a new constructor.

[JingsongLi]

There are Java invokers, so introduce this constructor.

[wuchong]

Thanks for the tip.

[wuchong]

LGTM. Only left a minor comment.

[wuchong]

LGTM.

Merging...