Lightning: Make sure we are using default block size of 16KB if user does not specify one. (#60097)

[ti-chi-bot]

This is an automated cherry-pick of #60097

What problem does this PR solve?

Issue Number: close #59947

Problem Summary:
Make we are using a sufficient default block size. Ref #49514

What changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

  To test the specific issue addressed in this PR, I used a ~1.4TB dataset consisting mostly of duplicate data. Before the fix, memory usage spiked during the ingest phase due to the large index metadata loaded by Pebble, causing OOM kills on a 16c64g VM. With the fix, memory consumption remained stable, staying below 17GB and leading to no disastrous memory spikes.

• 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

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.1@7b51a54). Learn more about missing BASE report.

Additional details and impacted files

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Flag	Coverage Δ
unit	71.2333% <100.0000%> (?)

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Components	Coverage Δ
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[OliverS929]

/retest

[Benjamin2037]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-03-20 09:18:01.027398649 +0000 UTC m=+519974.711634730: ☑️ agreed by Benjamin2037.
• 2025-03-24 07:53:00.929138432 +0000 UTC m=+860474.613374528: ☑️ agreed by D3Hunter.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, D3Hunter, wjhuang2016

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• lightning/OWNERS [Benjamin2037,D3Hunter]
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