Doctrine Relations

---
name: doctrine-relations
description: Define Doctrine entity relationships (OneToMany, ManyToMany, ManyToOne); configure cascade, orphan removal, multiple entity managers; prevent N+1 queries
capabilities: [read, search, edit, shell]
tags: [doctrine]
# projected by `bun run build` — do not edit by hand
allowed-tools:
  - Read
  - Glob
  - Grep
  - Write
  - Edit
  - Bash
---

# Doctrine Relations (Symfony)

## Use when
- Mapping a `ManyToOne`, `OneToMany`, `ManyToMany` or `OneToOne` and choosing the owning side.
- Deciding between `cascade` and `orphanRemoval` for child entities.
- A relation does not persist (only the inverse side was set), or `contains()` is slow on a large inverse collection.
- Splitting entities across several entity managers.

## Default workflow
1. Pick the owning side (holds the foreign key, `ManyToOne` with `inversedBy`) and the inverse side (`OneToMany` with `mappedBy`).
2. Initialize collections with `ArrayCollection` in the constructor, and write `addX()` and `removeX()` helpers that keep both sides in sync.
3. Use `cascade: ['persist']` for aggregates saved together, and `orphanRemoval: true` only for true composition.
4. Mark large inverse collections `fetch: 'EXTRA_LAZY'`, or test membership from the owning side.
5. Add fetch joins where a use case reads the relation, to avoid N+1 queries.
6. With several entity managers, keep each entity set in one manager and fetch repositories through `ManagerRegistry`.

## Guardrails
- Doctrine persists what the owning side holds: always set the `ManyToOne` reference.
- Avoid `cascade: ['remove']` on large collections (one DELETE per row), and never use `orphanRemoval` on shared entities.
- A relation cannot span two entity managers.
- For a non-default entity manager, fetch repositories with `ManagerRegistry::getRepository(Entity::class, 'name')`.

## Progressive disclosure
- Use this file for execution posture and risk controls.
- Open references when deep implementation details are needed.

## Output contract
- Entity mappings with the owning and inverse sides, cascade and orphan decisions.
- Fetch strategy for large collections and hot paths.
- Result of `doctrine:schema:validate`.

## References
- `reference.md`