feat: reduce a clone of string

[fengjiachun]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

As the title said

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Attention: Patch coverage is 87.27273% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 84.60%. Comparing base (8609977) to head (4a993cd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3422      +/-   ##
==========================================
- Coverage   85.01%   84.60%   -0.42%     
==========================================
  Files         889      889              
  Lines      146574   146596      +22     
==========================================
- Hits       124613   124028     -585     
- Misses      21961    22568     +607