Fix root document entityMap

[parada85]

Bug Report

Q	A
BC Break	no
Version	2.9.2

Summary

Problem class inheritance save in entitymap

How to reproduce

I have a simple class inheritance like this:

#[ODM\DiscriminatorMap([3 => Tag::class, 4 => Category::class])]
class Section {}


class Tag extends Section {}
class Category extends Section {}

Then I do something like this:

/** @var DocumentManager $manager */
$manager = Kernel::stGetObj()->getContainer()->get('doctrine_mongodb')->getManager();
$manager->getRepository(Section::class)->find(68);
$manager->getRepository(Section::class)->find(68);

It seems like two database queries are made, but only one should be executed since it should be cached in the entity map. The issue seems to be that when it looks up the entity map, it does so using the repository class, but then stores it with the actual class (the child class) instead.

18:33:35 DEBUG     [doctrine] MongoDB command: {"find":"section","filter":{"_id":68,"type":{"$in":[3,4]}},"limit":1,"$db":"db","lsid":{"id":{"$binary":"R5St6qBWSAqg\/2jT16lktA==","$type":"04"}}}
18:33:35 DEBUG     [doctrine] MongoDB command: {"find":"section","filter":{"_id":68,"type":{"$in":[3,4]}},"limit":1,"$db":"db","lsid":{"id":{"$binary":"R5St6qBWSAqg\/2jT16lktA==","$type":"04"}}}

However, if I do this:

/** @var DocumentManager $manager */
$manager = Kernel::stGetObj()->getContainer()->get('doctrine_mongodb')->getManager();
$manager->getRepository(Tag::class)->find(68);
$manager->getRepository(Tag::class)->find(68);

It works correctly, and only one query is made.

When fetching the same document twice, only one database query should be executed if the entity is already cached in the entity map, regardless of whether the parent or child class is used.

To resolve the issue, I have overridden the find method of the DocumentRepository and do the following:

$parentClass = $this->getReflectionParentClass(new \ReflectionClass($documentName));        
if ($map = $this->getDocumentManager()->getClassMetadata($parentClass->getName())->discriminatorMap) {
     foreach ($map as $class) {
        if ($ret = $this->getDocumentManager()->getUnitOfWork()->tryGetById($id, $this->getDocumentManager()->getClassMetadata($class))) {
            return $ret;
          }
     }
}

but method tryGetById is marked internal :(

[GromNaN]

Hello @parada85, thanks for the exhaustive description and the proposed fix.
I reproduced the error you reported and confirmed that your fix works.

This is also the same approach that is used in the ORM: https://github.com/doctrine/orm/blob/36bef3f959ea9f7f3ea370faf2c803b9be40f5d2/src/UnitOfWork.php#L1753-L1754

Also, could you add some tests to cover this feature?

[GromNaN]

Why do you need to add this condition?

[GromNaN]

Found the response here: #2725 (comment)

[GromNaN]

This need to be addressed and covered by tests: #2725 (comment)

I don't remember details about what is stored in rootDocumentName but at a glance now there can be a collision for COLLECTION_PER_CLASS inheritance type as it's perfectly possible for two separate documents to have same id

We can update the value of ClassMetadata::$rootDocumentName to contain $name when the strategy is COLLECTION_PER_CLASS. That would solve the issue. (Or an new internal property $identityMapName to keep backward compatibility).

@malarzm any idea?

I don't understand the purpose of COLLECTION_PER_CLASS, it looks the same as just extending the class as you cannot query the root repository. Having duplicate ids make it even more useless.

[malarzm]

I think I was using COLLECTION_PER_CLASS years ago to work around some mapped superclass limitations, but it's been so long I can't be sure.