advanced queuing - mongodb query without field name

Question

I would like query all objects that have a field containing a specific value. For example, I have two documents:

{"123": "apple", "217": "pear", "179": "orange"}
{"831": "pear", "189": "grapes"}

and would like to get all objects that has a field whose value is "apple", but I do not know the name of the field. Is it possible to specify a query in MongoDB to achieve this? (The numerical keys in the objects are children ids, and the values in the objects are long GUIDs)

Answer 1

Unfortunately, MongoDB does not support any method of querying all fields with a particular value. There is an existing Jira ticket requesting this enhancement: https://jira.mongodb.org/browse/SERVER-1248 . Feel free to comment, vote, or follow that ticket.

In the meantime, the usual way that this is handled is to change the MongoDB schema. For your example, you would change your existing schema:

{"123": "apple", "217": "pear", "179": "orange"} 
{"831": "pear", "189": "grapes"} 

And you might structure it something like this:

 { tags: [
        { cid: "123", value: "apple" },
        { cid: "217", value: "pear" },
        { cid: "179", value: "orange" },
      ]
    }
   { tags: [
        { cid: "831", value: "pear" },
        { cid: "189", value: "grapes" },
      ]
    }

Once you've done this, you can perform the follwing query to find all of the desired documents:

 db.docs.find( {'tags.value': "apple" } )

Note that this schema allows you to index the 'tags.cid' and 'tags.value' fields, which your original schema does not.

I hope this helps.

-William