How to bulk import entities with Doctrine?

Question

How to bulk import entities with Doctrine ?

Business requirements

I am using Doctrine 3 to bulk import a list of entities from a CSV.
Each row creates 100 entities~ and I flush it each 10 rows.
All entities are having a relationship with User (createUser)

But this is not this easy with the entity manager of Doctrine... For each solution I tried, I got an issue, so I ran out of solution and went here.

What I have tried ?

• Simply flush it
  => Run out of memory. When flushing entities, the unit of work keeps it in memory.
• Flush it and clear() all
  => Got error because the user was flushed and no more persisted, the entity is detached.

  [Doctrine\ORM\ORMInvalidArgumentException]                                                                                                                                                                                                                                                                        
  Multiple non-persisted new entities were found through the given association graph

• I tried to re-attach it
  => This feature is no more available
• Flush it and detach() entities one by one excluding user
  => Doctrine is failing and sometimes, some entities are not detached (This error is very complicated to solve cause of the randomness)
• Flush it, clear all and refresh persisted entities
  => This is a functional issue, this solution implies to set the user again in authentication system, clearing entities is killing it.

I could have more functional solutions but this harms the maintainability of the project.