ecto

name: ecto description: Ecto schemas, changesets, queries, and migrations. Use when working with the data layer, migrations, or repo. user-invocable: false

Ecto

When to Use

• Adding or changing Ecto schemas and changesets.
• Writing or refactoring context functions that use the repo (get, insert, update, delete, queries).
• Creating or reviewing migrations.
• Optimizing queries (preload, join, avoid N+1).

Principles

1. Schemas: In lib/my_app/ under the context. Use @primary_key, @foreign_key_type, @timestamps; use @enforce_keys for required fields. Keep changeset functions in the schema module or context.
2. Context API: Expose functions like get_user!(id), create_user(attrs), update_user(user, attrs) that return {:ok, struct} / {:error, changeset} or raise for get!-style APIs. Use the repo only inside context (or dedicated query modules).
3. Migrations: Create with mix ecto.gen.migration name. Do not edit migration files after they have been run in production. Add new migrations for further schema changes.
4. Queries: Prefer from for readability; use preload or join to avoid N+1. For complex queries, consider a dedicated query module.
5. Verification: After schema or migration changes, run mix ecto.migrate (in dev) and mix test. Do not modify existing migrations.