feat: impl label_join and label_replace for promql

[killme2008]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

#5151

What's changed and what's your intention?

Impl the following functions for PromQL:

• label_join
• label_replace

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

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[codecov]

Codecov Report

Attention: Patch coverage is 79.32692% with 43 lines in your changes missing coverage. Please review.

Project coverage is 83.80%. Comparing base (2137c53) to head (05e37f9).
Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5153      +/-   ##
==========================================
- Coverage   84.01%   83.80%   -0.22%     
==========================================
  Files        1172     1175       +3     
  Lines      218098   219174    +1076     
==========================================
+ Hits       183239   183669     +430     
- Misses      34859    35505     +646     

Copilot reviewed 1 out of 3 changed files in this pull request and generated 7 suggestions.

Files not reviewed (2)

• tests/cases/standalone/common/promql/label.result: Language not supported
• tests/cases/standalone/common/promql/label.sql: Language not supported

[dekelpilli]

It's worth noting that in PromQL, passing an empty string for label_replace's replacement argument will result in the label being removed. That is, if

{__name__="test",host="abc"} => test{host="abc",other_label="my_value"}

then

label_repalce({__name__="test",host="abc"}, "host", "", "", "", "") => test{other_label="my_value"}

I'm not sure if this would be handled downstream here, but I don't believe regexp_replace handles that.

[killme2008]

It's worth noting that in PromQL, passing an empty string for label_replace's replacement argument will result in the label being removed. That is, if

{__name__="test",host="abc"} => test{host="abc",other_label="my_value"}

then

label_repalce({__name__="test",host="abc"}, "host", "", "", "", "") => test{other_label="my_value"}

I'm not sure if this would be handled downstream here, but I don't believe regexp_replace handles that.

Thank you for your note; I'll test it now.

[killme2008]

@dekelpilli Looks like we can't remove the label in the current implementation right now. cc @waynexia

We don't know the replaced results until executing the plan, it's not easy to implement in the current planner.

I leave a todo and try to find a solution in the future.

[killme2008]

@waynexia @evenyag Ready for review, please take a look. Thanks @dekelpilli