ecto

Ecto is a domain-specific language and toolkit for data mapping and persistence in Elixir applications. It provides a consistent way to define how data is structured, loaded from and stored to a database, and how changes are validated and applied. Ecto focuses on a repository pattern and a composable query DSL, enabling developers to write database operations that are explicit, testable, and free from ad-hoc SQL.

Key components include the Ecto.Repo, which acts as a database wrapper; Ecto.Schema for mapping Elixir structs to database tables; Ecto.Changeset for validation, casting, and constraints; and Ecto.Query for building queries. Migrations are supported through Ecto.Migration to evolve database schemas over time.

Ecto supports associations (has_many, belongs_to), embeds for nested data, and preloading of associations to avoid N+1 queries. Changesets enable data cleansing and constraint enforcement, with features such as optimistic locking. The system is database-agnostic through adapters, with PostgreSQL being the most common backend, but other databases are supported through adapters.

Applications typically define schemas, write changesets, and interact with the database via Repo functions (insert, update, delete, get) and queries constructed with Ecto.Query. Ecto is commonly used with the Phoenix web framework as the primary persistence layer.