# Task Log - 2025-12-04-14-00 - Database Migration Implementation

## Actions
- Verified PostgreSQL database connectivity and current state (19 tables before migration)
- Added generated columns (tenant_id, kb_id) to all 9 LIGHTRAG_* tables
- Created 18 performance indexes on tenant_id and kb_id columns
- Created sync_tenant_from_workspace() trigger function
- Added auto-sync triggers to all 9 LIGHTRAG_* tables
- Dropped 8 unused tables (documents, entities, relations, embeddings, document_status, kv_storage, lightrag_tenants, lightrag_knowledge_bases)
- Created user_tenant_memberships table for RBAC
- Created schema_migrations tracking table
- Updated init-postgres.sql with clean schema (version 3.0.0)
- Updated DB_MODEL_AUDIT.md with implementation status
- Consolidated migration scripts in starter/migrations/

## Decisions
- Used HYBRID APPROACH: Keep LIGHTRAG_* tables as authoritative storage with generated columns
- Generated columns auto-extract tenant_id and kb_id from workspace column using SPLIT_PART
- Triggers auto-register tenants/KBs when data is inserted into any LIGHTRAG_* table
- Dropped unused "modern" tables that were never populated by the storage engine

## Final Schema
- **13 total tables** (reduced from 19)
  - 9 LIGHTRAG_* data tables (with generated columns)
  - tenants, knowledge_bases (metadata registry)
  - user_tenant_memberships (RBAC)
  - schema_migrations (tracking)
- **82 indexes** for query performance
- **9 auto-sync triggers** for tenant/KB registration
- **1,349 data rows** preserved intact

## Migrations Applied
| Version | Description | Status |
|---------|-------------|--------|
| 1.0.0 | Initial schema with LIGHTRAG_* tables | ✅ Applied |
| 2.0.0 | Add generated columns and indexes | ✅ Applied |
| 2.1.0 | Add auto-sync trigger | ✅ Applied |
| 2.2.0 | Create user_tenant_memberships | ✅ Applied |
| 3.0.0 | Drop unused tables | ✅ Applied |

## Files Modified
- `/starter/init-postgres.sql` - Clean schema with all features
- `/starter/migrations/002_add_generated_columns_fk.sql` - Consolidated migration
- `/starter/migrations/002_rollback_generated_columns_fk.sql` - Rollback script
- `/starter/migrations/003_drop_unused_tables.sql` - Drop unused tables
- `/DB_MODEL_AUDIT.md` - Updated with implementation status

## Lessons/Insights
- LIGHTRAG_* tables are the ACTUAL production storage, not "legacy" tables
- workspace format "{tenant_id}:{kb_id}" enables seamless multi-tenancy extraction
- Generated columns with SPLIT_PART provide zero-cost tenant isolation queries
- Auto-sync triggers ensure data consistency between workspace and metadata tables
