support scan concurrency hint for mock table

[windtalker]

Signed-off-by: xufei xufei@pingcap.com

What problem does this PR solve?

Issue Number: ref #6528

Problem Summary:

What is changed and how it works?

Add scan concurrency hint for mock table, so the concurrency of mock table scan is decided by dag_context.initialize_concurrency and the scan concurrency hint.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• SeaRise
• ywqzzy

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[ywqzzy]

/run-all-tests

[windtalker]

/merge

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 7b3d1d8