statistics: reduce small obj alloc for PreCalculateScalar (#52623)

[ti-chi-bot]

This is an automated cherry-pick of #52623

What problem does this PR solve?

Issue Number: close #52343

Problem Summary:

We don't need to re-alloc anything since we only read from the chunk, no modification after reading it.

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-8.1@5ccadf8). Click here to learn what that means.
The diff coverage is 100.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #52652   +/-   ##
================================================
  Coverage               ?   72.2573%           
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  Files                  ?       1468           
  Lines                  ?     426942           
  Branches               ?          0           
================================================
  Hits                   ?     308497           
  Misses                 ?      99141           
  Partials               ?      19304           

Flag	Coverage Δ
unit	71.1295% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9957% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	41.0761% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-16 16:22:51.368272338 +0000 UTC m=+355190.479318786: ☑️ agreed by winoros.
• 2024-04-17 02:57:57.789289553 +0000 UTC m=+393296.900336005: ☑️ agreed by hawkingrei.