How to query through a DBRef in MongoDB/pymongo?

reference mongodb pymongo dbref
Soviut picture Soviut · May 19, 2010 · Viewed 9.3k times · Source

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?

Answer

mdirolf picture mdirolf · May 19, 2010

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.

Related questions

MongoDB relationships: embed or reference?

I'm new to MongoDB--coming from a relational database background. I want to design a question structure with some comments, but I don't know which relationship to use for comments: embed or reference? A question with some comments, like stackoverflow, would …

Read More
How to query mongodb with DBRef

suppose I have the following datastructure: var user = {_id: 'foo', age: 35}; var post = {_id: '...', author: {$ref: user, $id: 'foo'},...}; How can I query all posts which references user[foo]? I tried the following but not work: db.post.…

Read More
How do I pass a variable by reference?

The Python documentation seems unclear about whether parameters are passed by reference or value, and the following code produces the unchanged value 'Original' class PassByReference: def __init__(self): self.variable = 'Original' self.change(self.variable) print(self.variable) def change(…

Read More