importer: only sample part of the files to get compression ratio

[joechenrh]

What problem does this PR solve?

Issue Number: close #64770

Problem Summary:

What changed and how does it work?

Only sample 1024 (maybe make it configurable) files for each compression type and use harmonic mean to get the average compression ratio.

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]

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