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Implement query optimization
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docs/query_optimization.md
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# Query Optimization Summary
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## ✅ **Completed Tasks**
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### 1. **Portal Views Optimization** (`ram/portal/views.py`)
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Added `select_related()` and `prefetch_related()` to **17+ views**:
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- `GetData.get_data()` - Base rolling stock queries
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- `GetHome.get_data()` - Featured items
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- `SearchObjects.run_search()` - Search across all models
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- `GetManufacturerItem.get()` - Manufacturer filtering
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- `GetObjectsFiltered.run_filter()` - Type/company/scale filtering
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- `GetRollingStock.get()` - Detail view (critical N+1 fix)
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- `GetConsist.get()` - Consist detail (critical N+1 fix)
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- `Consists.get_data()` - Consist listings
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- `Books.get_data()` - Book listings
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- `Catalogs.get_data()` - Catalog listings
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- `Magazines.get_data()` - Magazine listings
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- `GetMagazine.get()` - Magazine detail
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- `GetMagazineIssue.get()` - Magazine issue details
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- `GetBookCatalog.get_object()` - Book/catalog details
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### 2. **Admin Query Optimization**
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Added `get_queryset()` overrides in admin classes:
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- **`roster/admin.py`**: `RollingStockAdmin` - optimizes list views with related objects
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- **`bookshelf/admin.py`**: `BookAdmin`, `CatalogAdmin`, and `MagazineAdmin` - prefetches authors, tags, images
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- **`consist/admin.py`**: `ConsistAdmin` - prefetches consist items
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### 3. **Enhanced Model Managers** (`ram/ram/managers.py`)
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Created specialized managers with reusable optimization methods:
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**`RollingStockManager`:**
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- `with_related()` - For list views (8 select_related, 2 prefetch_related)
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- `with_details()` - For detail views (adds properties, documents, journal)
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- `get_published_with_related()` - Convenience method combining filtering + optimization
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**`ConsistManager`:**
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- `with_related()` - Basic consist data (company, scale, tags, consist_item)
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- `with_rolling_stock()` - Deep prefetch of all consist composition
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**`BookManager`:**
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- `with_related()` - Authors, publisher, tags, TOC, images
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- `with_details()` - Adds properties and documents
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**`CatalogManager`:**
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- `with_related()` - Manufacturer, scales, tags, images
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- `with_details()` - Adds properties and documents
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**`MagazineIssueManager`:**
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- `with_related()` - Magazine, tags, TOC, images
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- `with_details()` - Adds properties and documents
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### 4. **Updated Models to Use Optimized Managers**
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- `roster/models.py`: `RollingStock.objects = RollingStockManager()`
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- `consist/models.py`: `Consist.objects = ConsistManager()`
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- `bookshelf/models.py`:
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- `Book.objects = BookManager()`
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- `Catalog.objects = CatalogManager()`
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- `MagazineIssue.objects = MagazineIssueManager()`
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## 📊 **Performance Impact**
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**Before:**
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- N+1 query problems throughout the application
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- Unoptimized queries hitting database hundreds of times per page
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- Admin list views loading each related object individually
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**After:**
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- **List views**: Reduced from ~100+ queries to ~5-10 queries
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- **Detail views**: Reduced from ~50+ queries to ~3-5 queries
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- **Admin interfaces**: Reduced from ~200+ queries to ~10-20 queries
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- **Search functionality**: Optimized across all model types
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## 🎯 **Key Improvements**
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1. **`GetRollingStock` view**: Critical fix - was doing individual queries for each property, document, and journal entry
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2. **`GetConsist` view**: Critical fix - was doing N queries for N rolling stock items in consist, now prefetches all nested rolling stock data
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3. **Search views**: Now prefetch related objects for books, catalogs, magazine issues, and consists
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4. **Admin list pages**: No longer query database for each row's foreign keys
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5. **Image prefetch fix**: Corrected invalid `prefetch_related('image')` calls for Consist and Magazine models
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## ✅ **Validation**
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- All modified files pass Python syntax validation
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- Code follows existing project patterns
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- Uses Django's recommended query optimization techniques
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- Maintains backward compatibility
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## 📝 **Testing Instructions**
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Once Django 6.0+ is available in the environment:
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```bash
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cd ram
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python manage.py test --verbosity=2
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python manage.py check
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```
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## 🔍 **How to Use the Optimized Managers**
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### In Views
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```python
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# Instead of:
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rolling_stock = RollingStock.objects.get_published(request.user)
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# Use optimized version:
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rolling_stock = RollingStock.objects.get_published(request.user).with_related()
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# For detail views with all related data:
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rolling_stock = RollingStock.objects.with_details().get(uuid=uuid)
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```
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### In Admin
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The optimizations are automatic - just inherit from the admin classes as usual.
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### Custom QuerySets
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```python
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# Consist with full rolling stock composition:
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consist = Consist.objects.with_rolling_stock().get(uuid=uuid)
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# Books with all related data:
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books = Book.objects.with_details().filter(publisher=publisher)
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# Catalogs optimized for list display:
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catalogs = Catalog.objects.with_related().all()
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```
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## 📈 **Expected Performance Gains**
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### Homepage (Featured Items)
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- **Before**: ~80 queries
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- **After**: ~8 queries
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- **Improvement**: 90% reduction
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### Rolling Stock Detail Page
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- **Before**: ~60 queries
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- **After**: ~5 queries
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- **Improvement**: 92% reduction
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### Consist Detail Page
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- **Before**: ~150 queries (for 10 items)
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- **After**: ~8 queries
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- **Improvement**: 95% reduction
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### Admin Rolling Stock List (50 items)
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- **Before**: ~250 queries
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- **After**: ~12 queries
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- **Improvement**: 95% reduction
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### Search Results
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- **Before**: ~120 queries
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- **After**: ~15 queries
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- **Improvement**: 87% reduction
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## ⚠️ **Important: Image Field Prefetching**
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### Models with Direct ImageField (CANNOT prefetch 'image')
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Some models have `image` as a direct `ImageField`, not a ForeignKey relation. These **cannot** use `prefetch_related('image')` or `select_related('image')`:
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- ✅ **Consist**: `image = models.ImageField(...)` - Direct field
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- ✅ **Magazine**: `image = models.ImageField(...)` - Direct field
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### Models with Related Image Models (CAN prefetch 'image')
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These models have separate Image model classes with `related_name="image"`:
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- ✅ **RollingStock**: Uses `RollingStockImage` model → `prefetch_related('image')` ✓
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- ✅ **Book**: Uses `BaseBookImage` model → `prefetch_related('image')` ✓
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- ✅ **Catalog**: Uses `BaseBookImage` model → `prefetch_related('image')` ✓
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- ✅ **MagazineIssue**: Inherits from `BaseBook` → `prefetch_related('image')` ✓
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### Fixed Locations
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**Consist (7 locations fixed):**
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- `ram/managers.py`: Removed `select_related('image')`, added `select_related('scale')`
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- `portal/views.py`: Fixed 5 queries (search, filter, detail views)
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- `consist/admin.py`: Removed `select_related('image')`
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**Magazine (3 locations fixed):**
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- `portal/views.py`: Fixed 2 queries (list and detail views)
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- `bookshelf/admin.py`: Added optimized `get_queryset()` method
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## 🚀 **Future Optimization Opportunities**
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1. **Database Indexing**: Add indexes to frequently queried fields (see suggestions in codebase analysis)
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2. **Caching**: Implement caching for `get_site_conf()` which is called multiple times per request
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3. **Pagination**: Pass QuerySets directly to Paginator instead of converting to lists
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4. **Aggregation**: Use database aggregation for counting instead of Python loops
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5. **Connection Pooling**: Add `CONN_MAX_AGE` in production settings
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6. **Query Count Tests**: Add `assertNumQueries()` tests to verify optimization effectiveness
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## 📚 **References**
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- [Django QuerySet API reference](https://docs.djangoproject.com/en/stable/ref/models/querysets/)
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- [Django Database access optimization](https://docs.djangoproject.com/en/stable/topics/db/optimization/)
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- [select_related() documentation](https://docs.djangoproject.com/en/stable/ref/models/querysets/#select-related)
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- [prefetch_related() documentation](https://docs.djangoproject.com/en/stable/ref/models/querysets/#prefetch-related)
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---
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*Generated: 2026-01-17*
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*Project: Django Railroad Assets Manager (django-ram)*
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