How to add a new array field to collection in mongodb?

Question

For example, I have a collection, such as User, with one field name (and default _id field). I insert some documents to this collection.

Then I want to add a field emails (which is an array to insert multiple emails) to this collection. If it is a normal field (not is an array), it can do easy with update and $set. But, with the array, I cannot create a new field with update command and $upsert, $addToSet, $push... because the array has not created before.

I think this is a common behavior, but I cannot find any way to do that.

JohnnyHK · Accepted Answer · 2015-06-21 02:05:56Z

7

All of the $set, $addToSet, and $push operators will create the array if the field doesn't exist yet. Make sure you've added email to your Mongoose model's schema for the update to properly occur.

var userSchema = new Schema({
    name: String,
    emails: [String]
});

All three of the below options would have the same effect of adding the array of emails if the emails field doesn't exist yet or is empty:

var emails = ['[email protected]', '[email protected]'];
User.update({_id: id}, {$set: {emails: emails}}, function(err, num) {...});
User.update({_id: id}, {$addToSet: {emails: {$each: emails}}}, function(err, num) {...});
User.update({_id: id}, {$push: {emails: {$each: emails}}}, function(err, num) {...});

edited Jun 21, 2015 at 2:05

answered Jun 21, 2015 at 2:00

JohnnyHK

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1 Comment

t4nhpt Over a year ago

Thank, you save me. My mistake is I use $addToSet, but I push a single item to array, and it don't allow. Then I create an array and use $ set. Hooray, it work properly.

Sachin Shukla · Accepted Answer · 2015-06-21 15:51:30Z

-3

db.t1.insert({name:"sachin"})
db.t1.insert({name:"shukla"})
db.t1.update({}, {$set:{arr:[]}}, {multi:true} )
db.t1.update({}, {$push: {arr:"tmp"} }, {multi:true} )

Example

answered Jun 21, 2015 at 15:51

Sachin Shukla

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