planner: Set minimum cost to avoid parent multiplication cost discrepancies

[terry1purcell]

What problem does this PR solve?

Issue Number: ref #55126

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

[tiprow]

Hi @terry1purcell. Thanks for your PR.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.3437%. Comparing base (3922a4b) to head (af26ec6).
Report is 1 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #56387        +/-   ##
================================================
+ Coverage   73.3869%   75.3437%   +1.9568%     
================================================
  Files          1623       1623                
  Lines        447156     447197        +41     
================================================
+ Hits         328154     336935      +8781     
+ Misses        98887      89739      -9148     
- Partials      20115      20523       +408     

Flag	Coverage Δ
integration	48.8845% <100.0000%> (?)
unit	72.4725% <100.0000%> (-0.0082%)	⬇️

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

Components	Coverage Δ
dumpling	52.9478% <ø> (ø)
parser	∅ <ø> (∅)
br	52.3072% <ø> (+6.7796%)	⬆️

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, qw4990

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• pkg/planner/OWNERS [hawkingrei,qw4990]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-29 08:52:18.27655921 +0000 UTC m=+172093.696772222: ☑️ agreed by qw4990.
• 2024-09-29 09:01:00.163783487 +0000 UTC m=+172615.583996499: ☑️ agreed by hawkingrei.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #56411.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #56412.