memory: log task worker session - due dates, subtasks, task page

skills/app-builder/references/migrations.md

@@ -0,0 +1,49 @@
+# Database Migration Strategy
+
+## Drizzle ORM Migrations
+
+### Development (Local / Test)
+Use `db:push` for rapid iteration:
+```bash
+bun run db:push
+```
+This syncs schema directly — fast but destructive. Fine for dev/test.
+
+### Production
+Use `db:migrate` with generated migration files:
+```bash
+bun run db:generate  # creates SQL migration file
+bun run db:migrate   # applies migration
+```
+
+### Workflow
+1. Change schema in `src/db/schema.ts`
+2. Run `bun run db:generate` — creates migration in `drizzle/`
+3. Review the generated SQL
+4. Write rollback SQL in `drizzle/rollback/` (same filename)
+5. Test migration on staging
+6. Apply to production
+
+## Safe Migration Practices
+
+### Adding columns
+- Always add as nullable or with a default value
+- Never add non-nullable columns without defaults to tables with existing data
+
+### Removing columns
+- First deploy: stop reading/writing the column in code
+- Second deploy: remove the column from schema
+- Two-phase approach prevents errors during rolling deploys
+
+### Renaming columns
+- Don't rename directly — add new column, migrate data, remove old column
+
+### Adding indexes
+- Use `CREATE INDEX CONCURRENTLY` for large tables (avoids locks)
+- Drizzle may not generate concurrent indexes — check generated SQL
+
+## Backup Before Migration
+Always backup before production migrations:
+```bash
+pg_dump -Fc $DATABASE_URL > backup-$(date +%Y%m%d-%H%M%S).dump
+```