Hi 👋

Thanks for all the work on MikroORM, it’s been a great experience to use.

I’d love to have a $size operator for collection relations (OneToMany, ManyToMany, etc.) so we can filter entities based on the number of related items directly in the ORM filter syntax. For example:

// Restaurants with no reviews
em.find(Restaurant, { reviews: { $size: 0 } });

// Restaurants with at least 3 reviews
em.find(Restaurant, { reviews: { $size: { $gte: 3 } } });

// Users with between 1 and 5 roles
em.find(User, { roles: { $size: { $gt: 0, $lte: 5 } } });

This would make common patterns like “empty/non-empty relation” or “at least N related records” easy to express and very readable, in line with the existing operator style ($gt, $gte, $lte, etc.).

I think this would be a small but very impactful addition to the query API, especially for projects with a lot of relational filtering.

Thanks for considering it!