perf(etcd): refactor some code to improve performance

[xuruidong]

Description

Fixes # (issue)

Before:
The original code performed a cleanup of self.values and rebuilt self.values_hash by:

• Made a full copy of self.values
• Cleared the original and reinserted non-nil values
• Rebuilt values_hash in a separate step

Problems:

• Wasted memory (copied entire table)
• Slow (processed data twice)

Now:

1. In-place cleanup:
   • Removes nil values while keeping the same table
   • Updates values_hash at the same time
2. Trims empty space:
   • Deletes unused slots at the end

Why better?

• Faster: Does everything in one pass
• Uses less memory: No extra table copies
• Works better for big datasets

Before:
The original code performed a cleanup of self.values and rebuilt self.values_hash by:

• Made a full copy of self.values
• Cleared the original and reinserted non-nil values
• Rebuilt values_hash in a separate step

Problems:

• Wasted memory (copied entire table)
• Slow (processed data twice)

Now:

1. In-place cleanup:
   • Removes nil values while keeping the same table
   • Updates values_hash at the same time
2. Trims empty space:
   • Deletes unused slots at the end

Why better?

• Faster: Does everything in one pass
• Uses less memory: No extra table copies
• Works better for big datasets

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[juzhiyuan]

@xuruidong Just approved to run the CI

[xuruidong]

@xuruidong Just approved to run the CI

please run the CI again @juzhiyuan

[juzhiyuan]

@xuruidong Just approved to run the CI

please run the CI again @juzhiyuan

Hi @xuruidong, I couldn't find the Re-run button. Can you confirm the failed test cases?

[xuruidong]

I don't think the CI failure is related to the code changes.

[Baoyuantop]

Hi @xuruidong, can you add some descriptive information for PR?

[Baoyuantop]

Hi @xuruidong, please add a PR description so that others can review it better ~

[xuruidong]

Hi @xuruidong, please add a PR description so that others can review it better ~

Hi @Baoyuantop , the PR description has been added, please help review it. Thanks.

[Baoyuantop]

Please fix the failed ci

[xuruidong]

Please fix the failed ci

Hi @Baoyuantop ,please trigger the ci

[xuruidong]

Hi @Baoyuantop , the ci is not stable, the failed test should be rerun

[Baoyuantop]

Hi @xuruidong, there are still bad CIs that need to be fixed.

[Baoyuantop]

Hi @xuruidong, any updates?

[xuruidong]

Hi @xuruidong, any updates?

Hi @Baoyuantop ,please trigger the ci

[github-actions]

This pull request has been marked as stale due to 60 days of inactivity. It will be closed in 4 weeks if no further activity occurs. If you think that's incorrect or this pull request should instead be reviewed, please simply write any comment. Even if closed, you can still revive the PR at any time or discuss it on the [email protected] list. Thank you for your contributions.

[Baoyuantop]

Hi @xuruidong, are you still working on this pull request? There are some failed tests that need to be addressed.