doc: add Hash join v2 design doc

[windtalker]

What problem does this PR solve?

Issue Number: ref #53127

Problem Summary:

What changed and how does it work?

Add hash join v2 design doc

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @windtalker. Thanks for your PR.

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[windtalker]

/hold

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wshwsh12, XuHuaiyu

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-20 06:37:09.819877782 +0000 UTC m=+2067183.577013356: ☑️ agreed by wshwsh12.
• 2024-05-21 09:01:30.257944671 +0000 UTC m=+2162244.015080262: ☑️ agreed by XuHuaiyu.