主义mongoDB仅获得一个字段

Question

i have a this document:

[_id] => MongoId Object (
    [$id] => 542e6f6f10f0ed75138b4567
)
[description] => Lorem...
[lat] => 37.5184124
[lng] => 15.015836000000036
[name] => My company
[phone] => +4977665556
[photos] => Array (
    [0] => Array (
        [_id] => MongoId Object (
            [$id] => 542e6f7a10f0ed73138b4567
        )
        [image] => 06c2aeb0a8fbc03b7c77732166114a23.jpg
    )
    [1] => Array (
        [_id] => MongoId Object (
            [$id] => 542e6f7c10f0ed77138b4568
        )
        [image] => a7a428c48291137bade2fd81c842c5ab.jpg
    )
)

Now i want get only array photos with Doctrine ODM.

I tried this query, but not working:

$this->createQueryBuilder('Company')
            ->select('photos')
            ->field('ID')->equals($id)
            ->getQuery()
            ->getSingleResult();

This query return all document not only photos .

Why?

Answer 1

Using Builder::select() to project a specific field does not mean that the query will return that field alone. The Company's query builder will always return Company objects. In your case, getSingleResult() has the query return a single object instead of an iterable cursor of Company objects. The select() projection means that the MongoDB query will only return the _id and photos fields, which will then be hydrated into a Company object.

As a result, you'll find that Company::getName() probably returns null , while Company::getPhotos() probably returns a PersistentCollection of Photo objects. It's unclear to me from your example if those are referenced or simply embedded documents with an _id field.

By default, ODM hydrates query results. This can be problematic when you're using projections to exclude fields, as any further assignments to non-hydrated fields might be picked up as a change and persisted back to the database. If you're rather obtain the raw data, you can disable hydration with via Builder::hydrate() , which takes a boolean.

On a side note, I'd suggest you use 'id' or '_id' instead of 'ID' in your field() query. I'm not sure if ODM does a case-insensitive string comparison when it looks up mapped fields -- unless of course your PHP property is $ID , in which case you can ignore this suggestion.