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Related to Doctrine2 best practices : https://www.doctrine-project.org/projects/doctrine-orm/en/2.6/reference/best-practices.html

and related to that post : Why is it recommended to avoid bidirectional relations in ORM?

I need to understand if two unidirectional relations affects performances as much as one bidirectional relation, or less, or more.

As both types of relation result in the same SQL, performance issues seems to be related to hydration, persistance and DQL querying.

Like explained here : https://ocramius.github.io/blog/doctrine-orm-optimization-hydration/

Nicolas
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1 Answers1

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First, it is important to understand that perfomance issue occurs at PHP side and not at DBMS side.

Performance issues caused by bidirectionals relations are mainly related to two points :

  • hydration process of model's variables
  • DQL querying with many JOIN clauses

So the answer to the question is no. Even if you can achieve the same things with one bidirectional relation than you can achieve with two unidirectional relations, it's more performant to use one bidirectional because of optimizations in hydration process.

Nicolas
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