server: avoid reusing cached stmt ctx on cursor read (#40023)

[ti-chi-bot]

This is an automated cherry-pick of #40023

Signed-off-by: zyguan zhongyangguan@gmail.com

What problem does this PR solve?

Issue Number: close #39998

Problem Summary: The data race happens because the backgroud copr goroutines take a reference to memtracker of cached stmt ctx, and the cached stmt ctx will be reset on next COM_STMT_FETCH requests.

What is changed and how it works?

avoid reusing cached stmt ctx on cursor read.

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.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• LittleFall
• hawkingrei

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[hawkingrei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 9596975