If i have a mongo document id as a string how do I query for it as an _id?


If i have a mongo document id as a string how do I query for it as an _id?

Will it work correctly to do .find({_id:'stringID'}) or do I need to convert it to a bson object first?

4/20/2012 9:44:55 PM

Accepted Answer

Do you mean you have the 24 hex digit string of an ObjectId?

Assuming that's what you mean, most drivers have a way to take a string and convert it to an ObjectId. In JavaScript that's:

.find({_id:new ObjectId("4f91bfcfaa7c5687a0c686d4")})

Updated to be a bit more useful for the node-native driver (from the documentation at https://github.com/christkv/node-mongodb-native):

// Get the objectID type
var ObjectID = require('mongodb').ObjectID;

var idString = '4e4e1638c85e808431000003';
collection.findOne({_id: new ObjectID(idString)}, console.log)  // ok
collection.findOne({_id: idString}, console.log)  // wrong! callback gets undefined
4/21/2012 1:58:04 AM

If your _id values are strings, you may query them just like any other field. (Just remember, if you are setting custom values for _id, they must be kept unique, or you will get a duplicate key error. )

Here is an example in the Mongo JS Shell:

> db.test.insert({_id:"stringID1"})
> db.test.insert({_id:"stringID2"})
> db.test.insert({_id:"stringID3"})
> db.test.find({_id:"stringID1"})
{ "_id" : "stringID1" }

Is this what you were looking for? I hope I did not misunderstand your question!

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