AgentSkillsCN

slow-query-detector

检测Entity Framework Core代码库中的慢查询和性能问题。当分析数据库性能、查找N+1查询、识别缺失索引、审查存储库模式或优化EF Core查询时，可使用此技能。触发词包括“查找慢查询”、“检查N+1问题”、“分析数据库性能”、“审查查询性能”或“优化EF Core查询”。

SKILL.md
--- frontmatter
name: slow-query-detector
description: Detect slow queries and performance issues in Entity Framework Core codebases. Use when analyzing database performance, finding N+1 queries, identifying missing indexes, reviewing repository patterns, or optimizing EF Core queries. Triggers on requests like "find slow queries", "check for N+1 problems", "analyze database performance", "review query performance", or "optimize EF Core queries".

Slow Query Detector

Analyze EF Core codebases to detect slow queries and performance anti-patterns.

Quick Start

  1. •

    Run the analysis script to scan for common issues:

    bash
    python3 .claude/skills/slow-query-detector/scripts/analyze_efcore.py src
  2. •

    Review detected issues by severity (Critical > Warning > Info)

  3. •

    For each issue, check the suggested fix in references/patterns.md

Detection Workflow

Step 1: Automated Scan

Run the analysis script on the repository:

bash
python3 .claude/skills/slow-query-detector/scripts/analyze_efcore.py src

The script detects:

  • •N+1 query patterns (loops with await queries)
  • •ToListAsync followed by in-memory operations
  • •Missing AsNoTracking on read-only queries
  • •Unbounded queries (no Take/Skip)

Step 2: Manual Review

After automated scan, manually check:

  1. •Query Handlers - Search for QueryHandler.cs files and review foreach loops
  2. •Repository Methods - Check for methods that load all records
  3. •Include Chains - Look for missing .Include() calls

Use grep patterns:

bash
# Find foreach with await inside
grep -rn "foreach.*await" --include="*.cs"

# Find ToListAsync followed by LINQ
grep -rn "ToListAsync.*\." --include="*.cs"

# Find queries without AsNoTracking
grep -rn "await.*context\." --include="*.cs" | grep -v "AsNoTracking"

Step 3: Validate with EF Core Logging

Enable query logging in development to capture actual SQL:

csharp
// In Program.cs or DbContext configuration
optionsBuilder
    .UseNpgsql(connectionString)
    .LogTo(Console.WriteLine, LogLevel.Information)
    .EnableSensitiveDataLogging();

Common Patterns & Fixes

See references/patterns.md for detailed patterns including:

  • •N+1 Query Problem (Critical)
  • •Memory-based Aggregation (Critical)
  • •Missing Index Hints (Warning)
  • •Unbounded Result Sets (Warning)

Project-Specific Checks

For this university management system:

Known Issue Locations

  1. •GetStudentEnrollmentsQueryHandler - N+1 problem fetching course offerings per enrollment
  2. •SelectCourseOfferingsBySemesterQueryHandler - N+1 problem fetching courses per offering
  3. •CourseOfferingRepository.GetNextOfferingIdAsync - Loads all records for Max calculation
  4. •ClassSessionRepository.GetNextSessionIdAsync - Loads all records for Max calculation

Repository Pattern Review

Check all *Repository.cs files in:

  • •src/StudentRegistrations/Infrastructure/Persistence/Repositories/
  • •src/Enrollments/Infrastructure/Persistence/Repositories/
  • •src/Attendance/Infrastructure/Persistence/Repositories/

Index Verification

Review index definitions in:

  • •src/*/Infrastructure/Persistence/Configurations/*Configuration.cs
  • •src/*/Infrastructure/Persistence/Migrations/*.sql

Resources

scripts/

  • •analyze_efcore.py - Automated scanner for EF Core anti-patterns

references/

  • •patterns.md - Detailed slow query patterns with examples and fixes