Updating a embedded array in MongoDB

Question

I asked on a previous question on how to find entries in a embedded MongoDB document. Sitting with a new issue now. My structure looks like :

{
    "_id" : ObjectId("5260c4bd95f8e3ad08000000"),
    "ip" : "127.0.0.1",
    "services" : [ 
        {
            "port" : "22"
        }
    ]}

I want to add a new key/value pair to services.port where the port is 22, so that it looks like this :

{
    "_id" : ObjectId("5260c4bd95f8e3ad08000000"),
    "ip" : "127.0.0.1",
    "services" : [ 
        {
            "port" : "22",
            "product" : "ssh"
        }
    ]}

This is the update I run :

db.hosts.update({ "ip" : "127.0.0.1" }, { $addToSet : { services : { "port" : "22", "product" : "ssh" }}});

And this is what I am getting

{
    "_id" : ObjectId("5260c4bd95f8e3ad08000000"),
    "ip" : "127.0.0.1",
    "services" : [ 
        {
            "port" : "22"
        }, 
        {
            "port" : "22",
            "product" : "ssh"
        }
    ]}

Anyone know what I am doing wrong? Should I delete the entry and recreate it?

c.P.u1 · Accepted Answer · 2013-10-18 10:33:30Z

2

$addToSet performs a $push operation if the element doesn't exist. Since { "port" : "22", "product" : "ssh" } doesn't already exist in the services array, a new document is pushed to services.

db.hosts.update({ "ip" : "127.0.0.1" }, { $set: { "services.0.product": "ssh" }});

This uses '0' to reference the first element of the services array and set its product property to "ssh". It works because arrays are also objects with each index position being a property/key.

edited Oct 18, 2013 at 10:33

answered Oct 18, 2013 at 10:17

c.P.u1

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