Doctrine - Custom form field based on query

Question

I have 2 linked entities: User and Acess. I want my doctrine User entity to have a field that informs me if the user has acesses or not. I can't do a simple OneToMany relationship between the two tables, because there is thousands of acesses and it would be too costly to get thousands of records from the database once I only need to know if there is any. What I would want is a field linked to a native query like:

select * from accesses where user = <whatever> limit 1

More specifically, something like:

/**
 * USer
 *
 * @ORM\Table(name="user")
 * @ORM\Entity
 */
class User {

    /**
     * @ORM\Column(name="user_id", type="bigint", nullable=false)
     * @ORM\Id
     */
    private $id;

    /**
     * @ORM\Column(name="name", type="string", length=300, nullable=false)
     * @Assert\NotBlank()
     */
    private $name;

    /**
     * @ORM\Query="select exists (select id_acesses from accesses where user = "$id" limit 1)"
     */
    private $hasAcesses;
}

Is this possible ? is there another way to do this ?

Edit:

based on @Otanaught answer below, I have done some tests:

Using a OneToMany relation with EXTRA_LAZY fetch:

user-getAccesses()->isEmpty() selected the whole collection

user-getAccesses()->count() used count(*) in the database which took 243ms to return

for comparasion my query above who did what I want took 12ms in average with peeks of 2ms or even 1ms.

Maybe the good folks at doctrine could implement this at isEmpty for extra lazy queries ?

Thanx @Otanaught

Ota · Accepted Answer · 2014-07-18 12:34:39Z

1

Doctrine does not provide an annotation that allows you to specify a query for a property of an entity (Annotation reference). You could create a custom method in your repository to implement the check. Did you measure how costly the relation would be? With correct relations and indexes this should be a none issue, because doctrine lazy loads the relation? Check the doctrine documentation about extra lazy collections.

answered Jul 18, 2014 at 12:34

Ota

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9 Comments

Nelson Teixeira Over a year ago

well actually, reading this docs, extralazy association has what I need. It would be better still if I can access Collection's isEmpty method without triggering the load. Do you know if it's available ?

Ota Over a year ago

Actually calling count on extra lazy collections does not load the full collection. The documentation about extra lazy collections states this.

Nelson Teixeira Over a year ago

I have read. But it's that when working with large result sets, even a count can be constly. So that's why I thought in using isEmpty instead. But I'm testing. BRB in a couple of minutes with the results.

Ota Over a year ago

How do you want to check if something is there without asking? :) Even without an ORM this wouldnt be possible.

Nelson Teixeira Over a year ago

Well beacause it depends on the count() implementation. Se the query I gave as an example above ? For my needs it would be much less costly than any count estimate.

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