sqlite-data skill

---
name: sqlite-data
description: Use when working with SQLiteData library (@Table, @FetchAll, @FetchOne macros) for SQLite persistence, queries, writes, migrations, or CloudKit private database sync.
---

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