Dovodi_Backend/OPTIMIZATION_PLAN.md

Django Database Query Optimization Plan

Phase 1: Analysis Complete ✅

Current Issues Identified:

1. N+1 Query Problems in course, video, library, article, podcast views
2. Missing select_related/prefetch_related optimizations
3. Inefficient serializer methods with individual database queries
4. Missing database indexes on frequently queried fields
5. Suboptimal queryset patterns in views and admin

Phase 2: Query Optimization Implementation Plan

Step 1: Course App Optimization

Priority: HIGH (Core functionality)

1.1 Course Views Optimization

• CourseListAPIView: Add select_related for professor, category
• CourseDetailAPIView: Add prefetch_related for lessons, attachments, glossaries, participants
• MyCourseListAPIView: Optimize participant and completion queries

1.2 Course Serializers Optimization

• CourseListSerializer: Optimize professor and category access
• CourseDetailSerializer: Optimize all related object access
• CourseLessonSerializer: Optimize lesson completion and quiz queries

1.3 Course Admin Optimization

• CourseAdmin: Add select_related/prefetch_related to get_queryset
• ParticipantAdmin: Optimize student and course queries

Step 2: Video App Optimization

Priority: HIGH (Heavy content usage)

2.1 Video Views Optimization

• VideoListAPIView: Add prefetch_related for categories, collections
• VideoDetailAPIView: Optimize playlist and bookmark queries
• VideoCollectionViews: Optimize video relationships

2.2 Video Serializers Optimization

• VideoDetailSerializer: Optimize bookmark, rate, and playlist queries
• VideoCollectionSerializer: Optimize video access

Step 3: Library App Optimization

Priority: HIGH (Heavy content usage)

3.1 Library Views Optimization

• BookListView: Add prefetch_related for categories, collections
• BookDetailView: Optimize bookmark and rate queries
• BookCollectionViews: Optimize book relationships

3.2 Library Serializers Optimization

• BookSerializer: Optimize bookmark and rate queries
• BookCollectionSerializer: Optimize book access

Step 4: Article & Podcast Apps Optimization

Priority: MEDIUM

4.1 Similar patterns to Video/Library apps

• Apply same optimization patterns
• Focus on category and collection relationships
• Optimize bookmark and rate queries

Step 5: Account App Optimization

Priority: MEDIUM

5.1 User Admin Optimization

• UserAdmin: Already has some prefetch_related, enhance further
• StudentUserAdmin: Optimize course participation queries

Step 6: Chat App Optimization

Priority: MEDIUM

6.1 Chat Views Optimization

• RoomMessage queries: Add select_related for initiator, recipient, course
• ChatMessage queries: Add select_related for sender, room

Step 7: Bookmark & Rate System Optimization

Priority: HIGH (Used across all content types)

7.1 Bookmark Queries Optimization

• Optimize bookmark status checks in serializers
• Add bulk bookmark queries where possible

Phase 3: Database Indexing Plan

Step 1: Primary Indexes

• Add indexes on status fields (all models)
• Add indexes on created_at, updated_at fields
• Add indexes on slug fields

Step 2: Foreign Key Indexes

• Ensure all ForeignKey fields have indexes
• Add composite indexes for common query patterns

Step 3: Composite Indexes

• (user_id, service, status) for Bookmark model
• (course_id, student_id) for Participant model
• (status, created_at) for content models

Phase 4: Implementation Order

Week 1: Course App (Core functionality)

1. Course views optimization
2. Course serializers optimization
3. Course admin optimization
4. Add course-related indexes

Week 2: Content Apps (Video, Library)

1. Video app optimization
2. Library app optimization
3. Add content-related indexes

Week 3: Remaining Apps

1. Article and Podcast apps
2. Account app enhancements
3. Chat app optimization
4. Bookmark system optimization

Week 4: Final Optimizations

1. Remaining indexes
2. Performance testing
3. Query analysis and fine-tuning

Success Metrics

• Reduce average response time by 50-70%
• Reduce database query count per request by 60-80%
• Maintain exact same API response format
• Zero breaking changes to existing functionality

Implementation Strategy

• One optimization at a time
• Test each change individually
• Maintain backward compatibility
• Monitor performance improvements