fix: division by zero in leaderboard calculation

[mohansinghi]

Summary

Division by Zero in Leaderboard Calculation

Severity: Medium
File: crates/platform-server/src/db/queries.rs:341
Effort: Small (4 lines)

Current - can panic if scores vector is empty:

let consensus_score = scores.iter().sum::<f64>() / scores.len() as f64;

Impact: When scores vector is empty, division by zero causes panic and crashes the leaderboard update endpoint.

Fix: Add defensive check before division:

let consensus_score = if scores.is_empty() {
    0.0 // Should not happen due to check above, but defensive
} else {
    scores.iter().sum::<f64>() / scores.len() as f64
};

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Contribution by Gittensor, see my contribution statistics at https://gittensor.io/miners/details?githubId=158349177

Summary by CodeRabbit

• Bug Fixes
  • Improved leaderboard consensus-score calculation to defensively handle empty or missing evaluation data, avoiding errors and improving stability when processing incomplete data sets.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Updated update_leaderboard to return Ok(None) immediately when the evaluations list is empty; additionally, consensus_score computation now defensively handles an empty scores collection by using 0.0 as the fallback value.

Changes

Cohort / File(s)	Summary
Database query update crates/platform-server/src/db/queries.rs	Return Ok(None) early when evaluations is empty; compute consensus_score defensively by treating an empty scores collection as 0.0 to avoid invalid average calculations.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A cautious hop, a careful stare,

If no evaluations, I'll wait right there.
Empty scores? I set them to zero,
Safe averages so nothing goes hero.
🥕

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: fixing a division-by-zero bug in leaderboard calculations, which is the core issue addressed in the pull request.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a3bfd39 and e165d4c.

📒 Files selected for processing (1)

• crates/platform-server/src/db/queries.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• crates/platform-server/src/db/queries.rs

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[mohansinghi]

@echobt Could you please review my pr?