[Optimize] Support send batch parallelism for olap table sink

[caiconghui]

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[morningman]

How much is this performance improvement?

[caiconghui]

How much is this performance improvement?

This is the first step to speed up olap table sink. and the bottleneck for olaptable sink is still need to be deep solved.
I make a test in my environment with 5 node in cluster, query_timeout is 300

MySQL [test]> insert into info_p1 select * from info_p1;
ERROR 5024 (HY000): errCode = 2, detailMessage = Execute timeout
MySQL [test]> set send_batch_parallelism=1;
Query OK, 0 rows affected (0.00 sec)

MySQL [test]> set send_batch_parallelism=5;
Query OK, 0 rows affected (0.00 sec)

MySQL [test]> insert into info_p1 select * from info_p1;
Query OK, 84272656 rows affected (3 min 24.68 sec)
{'label':'insert_a88e439072c74d4b-927690bb54979af0', 'status':'VISIBLE', 'txnId':'76736'}

[morningman]

I think for any load job, if the user does not explicitly set the send_batch_parallelism parameter, the value of the session variable will be used by default.

[morningman]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.

[morningman]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.