server/tests/cursor: fix cursor fetch error flacky test

[YangKeao]

What problem does this PR solve?

Issue Number: close #47029

Problem Summary:

I finally found the root cause of this flacky test. It's easy to understand:

Success Path:

1. Execute the statement
2. Enable the failpoint
3. Fetch the statement
   3.1. The rowContainerReader worker works in the background, and return the error specified by failpoint

Fail Path:

1. Execute the statement
2. The rowContainerReader worker works in the background. At this time, the failpoint is still not enabled.
3. Enable the failpoint
4. Fetch the result, but get no error.

The rowContainerReader worker can run right after Execute command, because it has a channel buffer whose size is twice as the chunk size. By default, it's just 2048 (equals the whole table size in this test 🤦). Therefore, another fix of this issue is to increase the table size from 2048 to a higher value. But I choose to enable failpoint before executing the statement.

What changed and how does it work?

Enable the failpoint before executing the statement, so that it'll definitely trigger the failpoint.

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

[codecov]

Codecov Report

Merging #50969 (01ff83f) into master (ba77807) will increase coverage by 2.3746%.
Report is 3 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #50969        +/-   ##
================================================
+ Coverage   70.4569%   72.8316%   +2.3746%     
================================================
  Files          1466       1466                
  Lines        434160     436625      +2465     
================================================
+ Hits         305896     318001     +12105     
+ Misses       108961      98684     -10277     
- Partials      19303      19940       +637     

Flag	Coverage Δ
integration	49.2747% <ø> (?)
unit	70.4735% <ø> (+0.2290%)	⬆️

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

Components	Coverage Δ
dumpling	54.2940% <ø> (ø)
parser	∅ <ø> (∅)
br	51.1373% <ø> (+5.4496%)	⬆️

[bb7133]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-04 13:35:44.841303294 +0000 UTC m=+104670.408073176: ☑️ agreed by bb7133.
• 2024-02-04 14:03:17.135295803 +0000 UTC m=+106322.702065693: ☑️ agreed by Defined2014.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bb7133, Defined2014, lcwangchao

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[YangKeao]

/run-cherry-picker

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #53875.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #53876.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #53877.