planner: variable tidb_opt_enable_hash_join to skip hash join (#46575)

[ti-chi-bot]

This is an automated cherry-pick of #46575

What problem does this PR solve?

This PR adds a global/session knob to disable hash join, in order to prevent query plan regression.
Use cases:

• As an application developer, I’m very confident the queries don’t benefit from hash join. However, at times, bad plans were generated in which a hash join was selected. I will config the connection pool, and initialize the connections with set tidb_opt_enable_hash_join=no.
• As a DBA, I’m aware the application is OLTP workload, which works properly in MySQL ~5.7. I’m very sure the SQLs don’t need hash join. I’ve seen cases in the past. bad plans were generated in which a hash join was selected. After confirming with application developers, I will disable hash join in cluster level with set global tidb_opt_enable_hash_join=off

Issue Number: close #46695

What is changed and how it works?

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

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

Add a new global/session variable `tidb_opt_enable_hash_join` to control whether hash join is enabled or not.

[qw4990]

/test unit-test

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/test unit-test

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[qw4990]

/test unit-test

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@qw4990: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test unit-test

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@9f089b3). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-08 08:39:17.826528812 +0000 UTC m=+955155.413638952: ☑️ agreed by winoros.
• 2023-10-08 08:43:35.114780639 +0000 UTC m=+955412.701890795: ☑️ agreed by time-and-fate.

[easonn7]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: easonn7, time-and-fate, winoros, XuHuaiyu

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• OWNERS [XuHuaiyu,time-and-fate,winoros]

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