[DDC-128] Consider adding EntityManager#link/unlink methods for direct association manipulation Created: 07/Nov/09  Updated: 29/Dec/10

Status: Open
Project: Doctrine 2 - ORM
Component/s: ORM
Affects Version/s: 2.0-ALPHA2
Fix Version/s: 2.x
Security Level: All

Type: New Feature Priority: Major
Reporter: Roman S. Borschel Assignee: Roman S. Borschel
Resolution: Unresolved Votes: 1
Labels: None

Issue Links:
Reference
is referenced by DDC-546 New fetch mode EXTRA_LAZY for collect... Resolved

 Description   

A problem when working with collection-valued associations is that almost all operations except add($obj) require the collection to become initialized in order for the operation to be performed properly. While this is all correct and beautiful OO-wise it may be problematic at times with regards to performance. Hence we might want to consider to provide some convenient methods along the lines of link/unlink (name suggestions?) which allow more direct, less OO collection manipulation. Such methods obviously would bypass the normal object lifecycle and the changes done through these methods will not be reflected in the in-memory objects and collections, unless the user keeps them in-synch himself.



 Comments   
Comment by Benjamin Eberlei [ 11/Dec/09 ]

Questions

  • I suppose link and unlinked entities would then handled by UnitOfwork commit also?
  • Since the collection is not initialized, one does not know upfront if the action will be successful, what happens if:
    • an entity is linked with a collection, although they are already connected.
    • an entity is unlinked from a collection it is not in.

Regarding the naming, i like link/unlink.

Comment by Roman S. Borschel [ 17/Dec/09 ]

What do you mean by "handled by UnitOfWork commit" ? Whether the SQL is "scheduled" or executed immediately? Interesting question.
Scheduling would probably be better but also more difficult.

As far as usage is concerned, I currently imagine it as follows:

// EntityManager#link($sourceObj, $field, $targetObj)
$user = $em->getReference($userId); // $userId probably from request parameters
$address = $em->getReference($addressId); // $addressId probably from request parameters
$em->link($user, 'addresses', $address);

"What happens if: an entity is linked with a collection, although they are already connected."

Probably an SQL error which results in an exception from the driver. Depends on the database constraints though.

"What happens if: an entity is unlinked from a collection it is not in"

Probably nothing, at least not from the SQL side. An exception could be thrown from Doctrine itself if the update affected 0 rows.

Thanks for these initial questions. Thats definitely food for thought. Keep it coming.

Comment by Roman S. Borschel [ 26/Aug/10 ]

Pushed back.

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