Symfony: ManyToOne and Migration

Created at: 2023-05-17

Lately I had to migrate a csv and create the entity relative to them. I import them using the Id given by the csv, with the Id that when creating a ManyToOne relation I would spare some time.

Doctrine ManyToOne

Doctrine ManyToOne Relation allow to make a n..1 relation in your database, a common relation in mysql, see the Symfony explication.

In order to define, you can use Doctrine annotation:

or, when you are using symfony maker bundle, you can create automatically the annotation. Using the make bundle will automatically produce the oppposite relations: OneToMany.

you can pass some parameters when creating a ManyToOne Relation:

inversedBy:

cascade:

fetch:

Avoid findOneById

3 functions may be used in order to retrieve/emulate a relation in doctrine:

- find: retrieve an entity by peforming a findBy

- getReference: if the entity is already loaded, this will directly return the entity, otherwise, it will use the find functionality to give the entity.

- getPartialReference: for migrationstuff, this one is the one that we need, it creates a entity, with only the id, thus, in order to avoid creating a database request.

I had then a partial test: same request: creating the manyToOneRelation, using the three different types

- operation finds have been performed with

find: 145 ms

getReference: 117 ms

getPartialReference: 104 ms.

Reducing the overall time by 40ms.

there is a functionality in doctrine, called getReference:

To be considered

this functionality will throw errors, when the target entity does not exist, this could happen during the following cases:

- data insconsitency: the data you are migrating are faulty

- the relative entity is not created when you insert the new entity.