perf(sqlite-native): gate kv operation labels

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[NathanFlurry]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• fix(rivetkit): surface native sqlite kv errors to callers #4645
• fix(rivetkit): prevent sleep races during disconnect and db work #4644
• fix(rivetkit): isolate engine envoys and propagate startup failures #4643
• test(rivetkit): remove wasm sqlite-only fixtures and coverage #4642
• chore(sqlite-vfs): remove wasm sqlite packages and workspace wiring #4641
• chore(rivetkit): remove wasm sqlite runtime #4614
• fix(sqlite-native): restore native startup kv preload #4639
• fix(sqlite-native): delete metadata before chunk range #4638
• fix(sqlite-native): keep truncate cache coherent #4637
• fix(sqlite-vfs): use delete range for truncate cleanup #4636
• fix(sqlite-native): restore kv error hook #4635
• perf(sqlite-native): avoid cloning cached read chunks #4634
• perf(sqlite-native): gate kv operation labels #4633 👈 (View in Graphite)
• perf(sqlite-native): reuse read cache for partial writes #4632
• perf(sqlite-native): remove delete file existence probe #4631
• fix(sqlite-native): gate native read cache behind env var #4630
• fix(pegboard): isolate runner config dc lookup failures #4625 : 1 other dependent PR (#4626 )
• docs(pegboard): note runner config upsert split write risk #4624
• fix(pegboard): unpack global runner config keys correctly #4623
• fix(pegboard-gateway): enforce tunnel message state #4622
• fix(pegboard-runner): clear terminal tunnel routes #4621
• fix(pegboard): skip protocol version keys in runner pool backfill #4620
• fix(pegboard): create missing normal runner configs #4619
• fix(epoxy): reuse cached optimistic value #4618
• main

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[claude]

PR Review: perf(sqlite-native): gate kv operation labels

This is a focused, well-targeted performance improvement. The changes are correct and align with the codebase conventions.

Strengths

Removing std::env::var(RIVET_TRACE_SQL) calls on the hot path is the most impactful change. These were called on every KV operation and involve an OS syscall + string comparison each time. Eliminating them is a meaningful reduction in overhead.

Using format_args!() instead of format!() correctly avoids heap-allocating a String for the op label when DEBUG tracing is disabled. format_args! is lazy and only formats if the subscriber actually processes the event.

Removing eprintln! calls aligns with the CLAUDE.md guideline: never use eprintln!/println! for logging in Rust, always use tracing macros.

Suggestions

1. Timing overhead is still unconditional. Instant::now() and .elapsed() are called on every KV operation even when debug tracing is disabled. For zero overhead when debug is off, gate behind tracing::enabled!(tracing::Level::DEBUG). Instant::now is cheap so this is a micro-optimization, but worth noting.

2. Loss of RIVET_TRACE_SQL escape hatch. The env-var trace was useful for quick diagnostics without a configured tracing subscriber. Removing it means debug output now requires RUST_LOG=debug. This is the right direction per conventions, but worth noting in a dev guide.

3. Pre-existing: format string missing space. get({key_count}keys) produces output like get(5keys) - same as original. Out of scope here, but a minor follow-up cleanup would be get({key_count} keys).

Minor

The cosmetic reformatting of read_cache_enabled, existing_chunk, and flushed improves readability with no logic changes.

Overall this is a clean, correct perf fix. The main actionable suggestion is optionally gating the Instant calls, though low priority. LGTM.