CODEWITHSUNDEEP
pythonmongodbmongoengine
DachuanZhao
DachuanZhao

Reputation: 1349

How to insert after a element in a ListField with mongoengine in python?

I want to add a element in a ListField.Here is my code:

class Post(Document):
    _id = StringField()
    txt = StringField()
    comments = ListField(EmbeddedDocumentField(Comment))

class Comment(EmbeddedDocument):
    comment = StringField()
    comment_id = StringField()
    ...

...

insert_id = "3000"

update_comment_str = "example"

#query
post_obj = Post.objects(_id=str(_id)).first()

#find the element's position and update
position = 0
for position,_ in enumerate(post_obj.comments):
    if post_obj.comments[position].comment_id = insert_id:
        break;

post_obj.comments.insert(position+1,Comment(comment_id=str(len(post_obj.comments)+1),comment=update_comment_str)

#save
post_obj.save()

It's slow because I fetch the whole document into python instance .Then I save document.How to optimize it?

Upvotes: 0

Views: 1185

Answers (2)

bagerard
bagerard

Reputation: 6374

I believe you can do this with the push operator of mongoengine. e.g:

post = Post(comments=[Comment(comment='a'), Comment('c')]).save()
Post.objects(id=post.id).update(push__comments__1=[Comment(comment='b')])

Post.objects.as_pymongo() # [{u'_id': ObjectId('5cd49aa24ec5dc4cd7f5bbc8'), u'comments': [{u'comment': u'a'}, {u'comment': u'b'}, {u'comment': u'c'}]}]

If you don't know the position in advance, you can use an aggregate query to find it first:

# Find position
projection = {"index": { "$indexOfArray": [ "$comments.comment", 'c' ] }}
data = list(Post.objects(id=post.id).aggregate(
        {'$project': projection}))
position = data[0]['index']
# Push at position
key = "push__comments__{}".format(position)
Post.objects(id=post.id).update(**{key: [Comment(comment='b')]})

Upvotes: 2

Erdenezul
Erdenezul

Reputation: 597

in PyMongo, there is method called bulk_write to call update/insert/delete operations (http://api.mongodb.com/python/current/examples/bulk.html). Unfortunately, it is not supported in MongoEngine. But still, you can combine pymongo and MongoEngine.

Upvotes: 0

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