Revert "planner: fix leading hint cannot take effect in UNION ALL statements"

[hawkingrei]

Reverts #50145

What problem does this PR solve?

Issue Number: close #50067

Problem Summary:

What changed and how does it work?

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

[elsa0520]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-10 07:26:13.873668045 +0000 UTC m=+428163.457921718: ☑️ agreed by qw4990.
• 2024-01-10 07:30:28.666094784 +0000 UTC m=+428418.250348479: ☑️ agreed by elsa0520.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elsa0520, qw4990, winoros

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• OWNERS [elsa0520,qw4990,winoros]

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[codecov]

Codecov Report

Merging #50260 (027164e) into master (c55105e) will decrease coverage by 14.6281%.
The diff coverage is 100.0000%.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #50260         +/-   ##
=================================================
- Coverage   70.0079%   55.3799%   -14.6281%     
=================================================
  Files          1443       1554        +111     
  Lines        419685     586608     +166923     
=================================================
+ Hits         293813     324863      +31050     
- Misses       105557     239085     +133528     
- Partials      20315      22660       +2345     

Flag	Coverage Δ
integration	36.5519% <100.0000%> (?)
unit	70.0077% <100.0000%> (-0.0003%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	54.0269% <ø> (ø)
parser	∅ <ø> (∅)
br	55.4348% <ø> (+5.7934%)	⬆️

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #50268.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #50270.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #50272.

[ti-chi-bot]

/cherry-pick release-7.6

[ti-chi-bot]

In response to a cherrypick label: new pull request could not be created: failed to create pull request against pingcap/tidb#release-7.6 from head ti-chi-bot:cherry-pick-50260-to-release-7.6: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"No commits between pingcap:release-7.6 and ti-chi-bot:cherry-pick-50260-to-release-7.6"}],"documentation_url":"https://docs.github.com/rest/pulls/pulls#create-a-pull-request"}

[ti-chi-bot]

@ti-chi-bot: new pull request could not be created: failed to create pull request against pingcap/tidb#release-7.6 from head ti-chi-bot:cherry-pick-50260-to-release-7.6: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"No commits between pingcap:release-7.6 and ti-chi-bot:cherry-pick-50260-to-release-7.6"}],"documentation_url":"https://docs.github.com/rest/pulls/pulls#create-a-pull-request"}

In response to this:

/cherry-pick release-7.6

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