Mongodb only insert if value is unique, else update - in node.js

Question

I've started developing an app recently and have finally got my node.js server communicating with my mongodb database.

I want to insert a bunch a JSON objects that look something like this:

   {
    'Username': 'Bob',
    'longitude': '58.3',
    'latitude': '0.3'
   }

If this Object is inserted into myCollection, and then I try to insert an object again with the Username Bob, but with different coordinates, I want the latest 'Username': 'Bob' object to replace the earlier one. There can only be one object in myCollection with the 'Username': 'Bob' basically.

If this was a relational database I would make Bob a primary key or something, but I was wondering what the best way to do this with mongoDb would be. Should I use the update+upsert method? I tried that and it didn't seem to work!

Apologies if this seems like a silly question, but I am still new to all of this.

Anand Jayabalan · Accepted Answer · 2017-03-02 17:08:49Z

34

Yes, a simple update query with the upsert option should satisfy your use case:

db.collection.update(
   {username:"Bob"},
   {$set:{'longitude': '58.3', 'latitude': '0.3'}},
   { upsert: true}
)

When you run the above query the first time (i.e., Bob doesn't exist in the collection), a new document is created. But when you run it the second time with new values for lat/long, the existing document is updated with the new lat/long values.

You can also create a unique index on the username field to prevent multiple records for 'Bob' from being created even accidentally:

db.collection.ensureIndex( { "username": 1 }, { unique: true } )

EDIT:

db.collection.ensureIndex() is now deprecated and is an alias for db.collection.createIndex(). So, use db.collection.createIndex() for creating indexes

edited Mar 2, 2017 at 17:08

answered Apr 3, 2014 at 21:46

Anand Jayabalan

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4 Comments

DeaIss Over a year ago

Thanks! What if in the $set field I included the 'Username:Bob' field as well as the longitude and latitude? Also, does using ensure index of update have any benefits? Thanks again!

Anand Jayabalan Over a year ago

$set can include 'username':'Bob'. Except for the _id field, we can modify any other field. _id field is immutable. Yes, creating an index (even a non-unique one) will help in this case because we are querying the collection by username. If no index were present, it would be a full collection scan. Creating an index helps find the document quicker. You can specify the unique option if that's your requirement.

Victor Zamanian Over a year ago

As an update to this, db.collection.ensureIndex() is now deprecated, and is an alias for db.collection.createIndex().

WesternGun Over a year ago

If I have more than these fields, i.e., fields not unique, not included in query, neither want to change, which I want to insert if the query returns null, but want to keep the same when updating, where can I include them? In $set?

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