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ln-812-query-optimizer

Type: L3 Worker Category: 8XX Optimization Parent: ln-810-performance-optimization-coordinator

Fixes query efficiency issues found by ln-651-query-efficiency-auditor. Each fix verified via tests with keep/discard pattern. Metric: query count reduction (not runtime benchmark).

Overview

Aspect	Details
Input	Audit findings from `docs/project/persistence_audit.md` (ln-651 section) OR target file
Output	Optimized queries, verification report
Companion	ln-651-query-efficiency-auditor (finds issues) → ln-812 (fixes them)

Workflow

Phases: Pre-flight → Load Findings → Prioritize → Fix Loop → Report

Phase 0: Pre-flight Checks

Check	Required	Action if Missing
Audit findings OR target file	Yes	Block optimization
Test infrastructure	Yes	Block (need tests for verification)
Git clean state	Yes	Block (need clean baseline for revert)

MANDATORY READ: Load shared/references/ci_tool_detection.md — use Test Frameworks section for test detection.

Worktree & Branch Isolation

MANDATORY READ: Load shared/references/git_worktree_fallback.md — use ln-812 row.

Phase 1: Load Findings

From Audit Report

Read docs/project/persistence_audit.md, extract ln-651 findings:

Finding Type	Optimization
N+1 query	Batch loading / eager loading / `.Include()` / `prefetch_related`
Redundant fetch	Pass object instead of ID, cache result
Over-fetching	Select specific fields / projection / `.Select()`
Missing index hint	Add index annotation / migration
Unbounded query	Add `.Take()` / `LIMIT` / pagination

From Target File

If no audit report: scan target file for query patterns matching the table above.

Phase 2: Prioritize Fixes

Priority	Criteria
1 (highest)	N+1 in hot path (called per request)
2	Redundant fetches (same entity loaded multiple times)
3	Over-fetching (SELECT * where few columns needed)
4	Missing pagination on user-facing endpoints

Phase 3: Fix Loop (Keep/Discard)

Per-Fix Cycle

FOR each finding (F1..FN):
  1. APPLY: Edit query code (surgical change)
  2. VERIFY: Run tests
     IF tests FAIL → DISCARD (revert) → next finding
  3. VERIFY: Tests PASS → KEEP
  4. LOG: Record fix for report

Keep/Discard Decision

Condition	Decision
No tests cover affected file/function	SKIP finding — log as "uncovered, skipped"
Tests pass	KEEP
Tests fail	DISCARD + log failure reason
Fix introduces new N+1	DISCARD

Note: No benchmark needed — query optimization metric is correctness (tests pass) + structural improvement (fewer queries). The audit already identified the inefficiency.

Phase 4: Report Results

Report Schema

Field	Description
source	Audit report path or target file
findings_total	Total findings from audit
fixes_applied	Successfully kept fixes
fixes_discarded	Failed fixes with reasons
fix_details[]	Per-fix: finding type, file, before/after description

Configuration

Options:
  # Source
  audit_report: "docs/project/persistence_audit.md"
  target_file: ""               # Alternative to audit report

  # Verification
  run_tests: true

  # Scope
  fix_types:                    # Filter which types to fix
    - n_plus_one
    - redundant_fetch
    - over_fetching
    - unbounded_query

Error Handling

Error	Cause	Solution
No audit findings	ln-651 not run or no issues	Report "no findings to optimize"
ORM-specific syntax	Unknown ORM	Query Context7/Ref for ORM docs
Migration needed	Index addition requires migration	Log as manual step, skip

References

../ln-651-query-efficiency-auditor/SKILL.md (companion: finds issues)
shared/references/ci_tool_detection.md (test detection)

Definition of Done

Findings loaded from audit report or target file scan
Fixes prioritized (N+1 first, then redundant, over-fetch, unbounded)
Each fix applied with keep/discard: tests pass → keep, tests fail → discard
No new query inefficiencies introduced by fixes
Report returned with findings total, fixes applied, fixes discarded

Version: 1.0.0 Last Updated: 2026-03-08