dbref - Developer IT

How to manually create a DBRef using pymongo?

- by Soviut

I want to create a DBRef manually so that I can add an additional field to it. However, when I try to pass the following: {'$ref': 'projects', '$id': '1029412409721', 'project_name': 'My Project'} Pymongo raises an error: pymongo.errors.InvalidName: key '$id' must not start with '$' It would seem that pymongo reserve the $ for the special key, leading me to wonder if it is even possible to do what I'm trying to do?

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How to query through a DBRef in MongoDB/pymongo?

- by Soviut

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?

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Can DBRefs contain additional fields?

- by Soviut

I've encountered several situations when using MongoDB that require the use of DBRefs. However, I'd also like to cache some fields from the referenced document in the DBRef itself. {$ref:'user', $id:'10285102912A', username:'Soviut'} For example, I may want to have the username available even though the user document is referenced. This would provide me all the benefits of a single document approach; Faster querying and eliminating the need to do manual dereferencing in my code. While at the same time allowing me to use references where they make sense. The idea being that when the referenced document is updated (a user changes their name, for example) my business layer can automatically update all the documents that reference it. Ultimately, I'm wondering if it's considered good form to store additional fields on my DBRefs? Will it break anything? Will I lose my data each time a reference is rewritten? Will drivers like pymongo support it?

Developer IT