ORMet

ORMet is an open-source object-relational mapper designed to simplify database access by mapping relational data to in-memory domain models. It provides a code-first modeling approach in which developers declare models, fields, and relationships, and it supports migrations to evolve the database schema over time. The library emphasizes a lightweight API with a focus on portability across database engines.

ORMet supports multiple relational databases through adapters, with common targets including PostgreSQL, MySQL, and SQLite. It offers a fluent API for defining models and relationships, a query builder for composing SQL expressions, and support for both lazy and eager loading of associations. A unit-of-work pattern manages transactional boundaries, and a migrations subsystem provides reversible change scripts to evolve the schema.

Architecture-wise, ORMet consists of a core ORM engine that handles identity maps, session management, and transaction scoping, together with pluggable database adapters. The design favors a data mapper approach, enabling isolation between domain models and persistence concerns, while allowing optional use of a repository-like pattern by developers.

History and development: The project is maintained by an open-source community, with contributions from individual developers and organizations. It aims for portability, testability, and a predictable performance profile suitable for small to mid-sized applications.

Usage and reception: ORMet is commonly used in projects that require rapid data access layers without full-stack ORMs. It has an active but modest ecosystem of plugins, tutorials, and community support; some users note that performance can be less predictable than hand-tuned SQL or micro-ORMs.

See also: Object-relational mapping, Active Record, Data mapper, Query builder.