MongoDB in nodejs and the update/upsert command

So I ran into a weird issue, which in hindsight makes perfect sense. While trying to issue an "upsert" command (which is apparently similar to a REPLACE command in legit-SQL; insert the record if not found, otherwise update it's values/columns appropriately), it was dying. Here's my flow:

// attempt to open connection; run update-crud operation
__open(function(err, db) {
    __getCollection(db, collection, function(collection) {
        collection.update(
            spec,
            obj,
            {
                upsert: true,
                multi: true,
                safe: false
            },
            callback || function(){}
        );
    });
});

This code follows the following flow:

• Open a connection to mongo
• Grab the collection specified
• Issue an update command
• Pass in a spec object which defines the query/where clause for what should be
• updated if it exists
• Pass in the object values
• Set some options (eg. that an upsert should occur; that all documents matching
• spec should be used; perform check to see if the operation failed.
• Call callback if specified

Seems legit. It all follows the docs a'la the node-mongodb-native package on github. After testing, I found the problem was that I was specifying multi: true.

In hindsight, it makes sense. In the above logic, I was writing out that if a matching "record" was found, update it. I was hoping that if one wasn't found, it should insert it. But how would multi: true work? This flag can only be specified when upsert is set to false. Otherwise, it wouldn't know how many "records" to insert.

Hopefully this saves someone else a little bit of time.