[FLINK-21664][table-api] Support STATEMENT SET syntax in TableEnvironment

[SteNicholas]

What is the purpose of the change

Currently we have discussed the grammar about multi-line statements as follows:

BEGIN STATEMENT SET;
INSERT INTO ... SELECT ...;
INSERT INTO ... SELECT ...;
END;

SqlParser should support STATEMENT SET syntax in TableEnvironment.

Brief change log

• Add SqlStatementSet to support STATEMENT SET syntax for SqlParser.

Verifying this change

• FlinkSqlParserImplTest adds testStatementSetWithSingleInsertInto, testStatementSetWithMultiInsertInto, testStatementSetWithoutInsertInto and testStatementSetWithCreateTable to verify whether SqlParser supports the STATEMENT SET syntax.

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• Dependencies (does it add or upgrade a dependency): (yes / no)
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• 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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[fsk119]

Thanks for your contribution @SteNicholas.

I have some thoughts about this PR. Because our goal is to submit statement set in the sql client. However, the Executor is just a wrapper of the TableEnvironment that can notice the Operation rather than SqlNode. Therefore, we need to introduce operations.

The second question is how sql client submits statement. In the FLIP, we reach consensus that the desired behaviour looks like

Flink SQL> BEGIN STATEMENT SET;
 
[Info] Begin the statement set.
 
Flink SQL> INSERT INTO emps1 SELECT * FROM emps(x, y);
 
[Info] Add the statement into the statement set.
 
Flink SQL> INSERT INTO emps2 SELECT * FROM emps(x, y);
 
[Info] Add the statement into the statement set.
 
Flink SQL> END;
 
[Info] Submitting SQL statement set to the cluster...

I think the proposed grammer may not achieve the final goal.

[SteNicholas]

@wuchong @fsk119 , I have followed the statement set syntax as follows:

BEGIN STATEMENT SET;
INSERT INTO xx SELECT * FROM xxx;
END;

Please help to review this update for the statement set syntax.

[SteNicholas]

@wuchong , thanks for detailed review. I have followed your comments and only supported the statement set parser. Please help to review again.

[wuchong]

LGTM