Using find() to search for nested keys in MongoDB

Question

This is going to be a silly question, but if I have a Mongo object that is in this format:

{
    "url": "google.com",
    "statusCode": 301,
    "headers": {
        "location": "http://www.google.com/",
        "content-type": "text/html; charset=UTF-8",
        "date": "Fri, 22 Mar 2013 16:27:55 GMT",
        "expires": "Sun, 21 Apr 2013 16:27:55 GMT",
        "cache-control": "public, max-age=2592000",
        "server": "gws",
        "content-length": "219",
        "x-xss-protection": "1; mode=block",
        "x-frame-options": "SAMEORIGIN"
    }
}

Using db.collections.find(), how do I find the server key, or any key that is nested within another key?

I have tried db.collections.find({headers:{server:"gws"}})

I have tried quoting them in all possible combinations, but the output has always been blank, or ...

Any suggestions would be appreciated.

Great question! All pymongo tutorials never use a nested key! — Robert Alexander
– Robert Alexander, Commented Feb 16, 2023 at 8:50

Aaron Dufour · Accepted Answer · 2013-03-22 16:40:50Z

26

You have to use dot notation to get what you're looking for. It would look like:

db.collections.find({"headers.server":"gws"})

In your query, what you're asking for is documents where headers is an object that looks like {server: "gws"}, so that only work if you know what the entire subdocument is.

answered Mar 22, 2013 at 16:40

Aaron Dufour

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3 Comments

galeej Over a year ago

will this work smoothly even when there are large user datasets?

Aaron Dufour Over a year ago

@galeej Sorry, I haven't used Mongo in 7 years so I'm no longer very familiar with the performance characteristics. I suspect that it will be quite fast as long as the field you're querying is indexed, though.

Robert Alexander Over a year ago

Very useful answer as PyMongo examples only use a shallow dict

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