CODEWITHSUNDEEP
referencemongodbpymongodbref
Soviut
Soviut

Reputation: 91724

How to query through a DBRef in MongoDB/pymongo?

Is it possible to query through a DBRef using a single find spec?

user collection

{
    'age': 30
}

post collection

{
    'user': DBRef('user', ...)
}

Is it possible to query for all post who's users are 30 in a single find step? If not, would it be wise to create a javascript function to handle the multi-stage operation or will that cause blocking problems?

Upvotes: 5

Views: 11301

Answers (3)

Rinat Mukhamedgaliev
Rinat Mukhamedgaliev

Reputation: 5731

Install python bson package. and try as example. 

import pymongo
from pymongo import MongoClient
from bson.dbref import DBRef

client = MongoClient('ip', 27017)

client.the_database.authenticate('user', 'password', source='db_name')
db = client['db_name']
user = db['user']
user_id = user.find_one({'email': '[email protected]'}).get('_id')

client_user_relation = db['client_user_relation']
print(client_user_relation.find_one())
print(user_id)
print(DBRef(collection = "user", id = user_id))
print(client_user_relation.find_one({'user': DBRef(collection = "user", id = user_id)}))

Upvotes: 0

MFB
MFB

Reputation: 19837

I use a Python driver, so forgive my not-so-mongodb syntax:

users = list(db.Users.find({'Age':30}))
posts = list(db.Posts.find({'User':{'$in':users}}))

Upvotes: 1

mdirolf
mdirolf

Reputation: 7651

it's not possible to do that. i would recommend either:

a) changing your data model so that all of the data is in a single document (might not be possible depending on your case).

b) querying for users who are 30 first, and then doing a second query to get posts where user is $in that list. i would do this client side rather than using server-side JS or anything like that.

Upvotes: 6

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