Agent Skills: SQLite Data

SQLite Data

SQLiteData provides type-safe SQLite access through Swift macros, simplifying database modeling and queries while handling CloudKit sync, migrations, and async patterns automatically.

Reference Loading Guide

ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.

| Reference | Load When | |-----------|-----------| | Table Models | Defining tables with @Table, setting up primary keys, columns, or enums | | Queries - Basics | Using @FetchAll, @FetchOne, @Selection, filtering, ordering, or joins | | Queries - Advanced | Using @Fetch with FetchKeyRequest, dynamic queries, recursive CTEs, or direct reads | | Writes | Inserting, updating, upserting, deleting records, or managing transactions | | Views - SwiftUI | Using @FetchAll/@FetchOne in SwiftUI views, @Observable models, or animations | | Views - Integration | UIKit integration, dynamic query loading, TCA integration, or observe {} | | Migrations | Creating database migrations with DatabaseMigrator or #sql() macro | | CloudKit Sync | Setting up CloudKit private database sync, sharing, or sync delegates | | Dependencies | Injecting database/sync engine via @Dependency, bootstrap patterns, or TCA integration | | Testing | Setting up test databases, seeding data, or writing assertions for SQLite code | | Advanced - Queries | Implementing triggers, custom database functions, or full-text search (FTS5) | | Advanced - Optimization | Performance tuning, indexes, custom aggregates, JSON aggregation, or self-joins | | Schema Composition | Using @Selection column groups, single-table inheritance, or database views |

Core Workflow

When working with SQLiteData:

1. Define table models with @Table macro
2. Use @FetchAll/@FetchOne property wrappers in views or @Observable models
3. Access database via @Dependency(\.defaultDatabase)
4. Perform writes in database.write { } transactions
5. Set up migrations before first use

Common Mistakes

1. N+1 query patterns — Loading records one-by-one in a loop (e.g., fetching user then fetching all their posts separately) kills performance. Use joins or batch fetches instead.

2. Missing migrations on schema changes — Modifying @Table without creating a migration causes crashes at runtime. Always create migrations for schema changes before deploying.

3. Improper transaction handling — Long-running transactions outside of database.write { } block can cause deadlocks or data loss. Keep write blocks short and focused.

4. Ignoring CloudKit sync delegates — Setting up CloudKit sync without implementing SyncDelegate means you miss error handling and conflict resolution. Implement all delegate methods for production.

5. Over-fetching in SwiftUI views — Using @FetchAll without filtering/limiting can load thousands of records, freezing the UI. Use predicates, limits, and sorting to keep in-memory footprint small.