DDC-2250: Joining Associations in Single Inheritance Scheme #2831

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admin · 2026-01-22T14:05:11+01:00

admin commented

2026-01-22 14:05:11 +01:00

Originally created by @doctrinebot on GitHub (Jan 20, 2013).

Originally assigned to: @beberlei on GitHub.

Jira issue originally created by user johannes:

Let's assume the following class hierarchy:

AbstractComment
SpecialComment extends AbstractComment
{
    private $specialAssociation;
}
RegularComment extends RegularComment

Now, I'd like to write a query such as:

SELECT c, a FROM AbstractComment c LEFT JOIN c.specialAssociation a

The idea is to preload the association when selecting all comments. Now, that association is only present on a sub-class of the queried class, but since it is a single table inheritance, Doctrine should be able to join it for those entities where it is present.

At the moment unfortunately, Doctrine shows an error that the association does not exist on the AbstractComment class. Also, there is no real alternative to this except moving the collection to the base class even if it does not belong there.

Originally created by @doctrinebot on GitHub (Jan 20, 2013). Originally assigned to: @beberlei on GitHub. Jira issue originally created by user johannes: Let's assume the following class hierarchy: ``` AbstractComment SpecialComment extends AbstractComment { private $specialAssociation; } RegularComment extends RegularComment ``` Now, I'd like to write a query such as: ``` SELECT c, a FROM AbstractComment c LEFT JOIN c.specialAssociation a ``` The idea is to preload the association when selecting all comments. Now, that association is only present on a sub-class of the queried class, but since it is a single table inheritance, Doctrine should be able to join it for those entities where it is present. At the moment unfortunately, Doctrine shows an error that the association does not exist on the AbstractComment class. Also, there is no real alternative to this except moving the collection to the base class even if it does not belong there.

admin added the Bug label 2026-01-22 14:05:11 +01:00

admin closed this issue

2026-01-22 14:05:12 +01:00

admin commented

2026-01-22 14:05:13 +01:00

@doctrinebot commented on GitHub (Jan 20, 2013):

Comment created by @beberlei:

DQL has strict typing with regard to inheritance, this type of query is not possible.

@doctrinebot commented on GitHub (Jan 20, 2013): Comment created by @beberlei: DQL has strict typing with regard to inheritance, this type of query is not possible.

admin commented

2026-01-22 14:05:13 +01:00

@doctrinebot commented on GitHub (Jan 20, 2013):

Issue was closed with resolution "Can't Fix"

@doctrinebot commented on GitHub (Jan 20, 2013): Issue was closed with resolution "Can't Fix"

admin commented

2026-01-22 14:05:13 +01:00

@doctrinebot commented on GitHub (Jan 20, 2013):

Comment created by johannes:

A too bad. I guess the code around inheritance is already quite complex that it does not make sense to add an exception for this case.

Do you think it would somehow (maybe manually) be possible to load collections in a batch operation? For example, something like this:

$batch = array();
foreach ($comments as $comment) {
    if ($comment instanceof SpecialComment) {
        $batch[] = $comment->getSpecialAssociation();
    }
}

$this->em->batchLoad($batch);

@doctrinebot commented on GitHub (Jan 20, 2013): Comment created by johannes: A too bad. I guess the code around inheritance is already quite complex that it does not make sense to add an exception for this case. Do you think it would somehow (maybe manually) be possible to load collections in a batch operation? For example, something like this: ``` $batch = array(); foreach ($comments as $comment) { if ($comment instanceof SpecialComment) { $batch[] = $comment->getSpecialAssociation(); } } $this->em->batchLoad($batch); ```

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Reference: doctrine/archived-orm#2831