How do you delete an embedded document using Mongoengine?

Question

I have a collection that has an EmbeddedDocumentField. I'm having trouble finding examples of how to delete an embedded document from the collection. Can someone provide me with an example or reference to one?

Here is what my setup looks like:

• Python 2.7.5
• Django 1.5.5
• MongoEngine 0.8.7

Code:

class Merchant(Document):
    merchant_id = StringField(max_length=50)
    merchant_name = StringField(max_length=150)
    merchant_name_search_alias = StringField(max_length=150)
    website = StringField(max_length=150)
    location = ListField(EmbeddedDocumentField(Location))
    address = StringField(max_length=50)
    city = StringField(max_length=30)
    state = StringField(max_length=20)
    zipcode = IntField()
    phone_nummber = StringField(max_length=10)
    sub_lat = FloatField()
    sub_lng = FloatField()
    country = StringField(max_length=20)
    promotion = ListField(EmbeddedDocumentField(Promotion))


class Promotion(EmbeddedDocument):
    provider_name = StringField(max_length=50)
    provider_website = URLField()
    promo_name = StringField(max_length=300)
    promo_name_search_alias = StringField(max_length=100)
    retail_price = DecimalField(precision=2, force_string=True)
    discount_price = DecimalField(precision=2, force_string=True)
    deal_url = URLField()
    buy_url = URLField()
    deal_image_url = URLField()
    description = StringField(max_length=1000)
    start_at = DateTimeField()
    end_at = DateTimeField()
    category = StringField(max_length=50)
    dq_category = StringField(max_length=50)
    keywords = StringField(max_length=100)

Hoxie

Can you just update the outer document and set the embedded document to null? AFAIK an embedded document is just a field that happens to be a subtree. – Suellen

I haven't tried that but seems like that would work. I'm new to MongoDB and MongoEngine so wasn't sure if there was a "proper" way to do it. Thanks! – Hoxie

Answer 1

You can $unset a field using MyDoc.objects.update(unset__myField=1) Or using $pull to remove a single value from a list eg: MyDoc.objects.update(pull__myField=Value)

See: https://docs.mongoengine.org/guide/querying.html?highlight=unset#atomic-updates

Metalinguistics

@Metalinguistics could you help me with this? – Requisite

@Metalinguistics I'm facing the issue I need solution. but, the URL you have provided above is not available. Kindly do help me – Inflexible

is Value in this case the embedded document to be removed? – Teddy

Answer 2

user = User_.objects(username=username).get()
for ad in user.ads:
    if str(ad["_id"]) == id:
        user.ads.remove(ad)
user.save()

this is the only way i found to remove a value from an array of embeded doc

Lindsy

Be careful with this approach, if you delete a lonely document inside the list, you also delete the list. Furthermore, in the latest versions, you should use oid instead of _id. Better to use pull_adds__oid as explained by @Ross. – Centrifugal