Cloud Parts

Full ORMs

Map classes to tables and manage the objects for you: one object per row in a session, change tracking, saving a whole unit of work at once, lazy loading and migrations.

How they work

A full ORM keeps state between your code and the database. A Hibernate session (its persistence context) and an EF Core DbContext (its change tracker) both track every entity loaded through them, and when the session flushes or SaveChanges runs, the ORM works out the INSERT, UPDATE and DELETE statements for whatever changed. SQLAlchemy’s ORM does the same with a unit of work built on its Core layer, and Rails’ Active Record puts load and save methods on each model object instead.

That buys a lot of saved code for applications with rich domain models and many forms, and the price is magic you have to understand: lazy relations that fire extra queries, automatic flushes before queries, and sessions that must not live too long. Prisma sits at the light end of this kind. It generates a typed client from a schema file and handles relations and migrations, but returns plain objects with no session or change tracking.

Technologies

What all object-relational mapping have in common →
Active Record (Ruby on Rails)Open sourceThe model layer of Ruby on Rails and the best-known implementation of Fowler’s Active Record pattern: each Ruby class wraps a table, each object a row, and objects load, validate and save themselves.Entity Framework CoreOpen sourceMicrosoft’s object-relational mapper for .NET: you query C# classes with LINQ, a `DbContext` tracks the entities it loads, and `SaveChanges` writes every change back as SQL through a pluggable database provider.Hibernate ORMOpen sourceThe standard object-relational mapper for Java: it maps annotated classes to tables, tracks changes to loaded objects in a session and writes them back as SQL, and implements Jakarta Persistence (JPA).Prisma ORMOpen sourceA TypeScript ORM driven by a schema file: you declare models once, Prisma generates a fully typed client and SQL migrations from them, and queries return plain JavaScript objects.SQLAlchemyOpen sourceA Python database toolkit in two layers: a SQL expression layer (Core) that builds and runs SQL, and an ORM on top of it that maps classes to tables with an identity map and a unit of work.Tortoise ORMOpen sourceAn async-native Python ORM with a Django-style API: models as classes, `await Model.filter(...)` queries, and built-in migrations since 1.0.

Sources

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