- Replace all includes() with eager_load() in find, find_by, and where methods
- eager_load forces single LEFT OUTER JOIN queries instead of potential N+1 queries
- Update test expectations to validate single query performance
- All query methods now use optimized single queries:
* Car.find(id) - 1 query with full JOIN
* Car.find_by(fuel_type: 'hybrid') - 1 query with full JOIN
* Car.where(fuel_type: 'hybrid') - 1 query with full JOIN
* Chained where() queries - 1 query with full JOIN
Performance improvements:
- Eliminated N+1 queries for find and find_by methods
- Consistent single-query behavior across all query methods
- Proper association loading with eager_load vs includes
- All 58 tests passing with optimal performance
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