Add new field to an Array of type object to a collection in MongoDB

Question

See example below (json format from mongochef). I need to add a new field to each element in our collection called isReadOnly (bool). How would I do this? I can easily add it to the root of the document but battling to do it within each array element.

{ 
"_id" : "fda42f22-0fa4-4e4a-94bf-245b1124c8b9", 
"_t" : "FullConfiguration", 
"DeviceConfigName" : "Illinois", 
"Elements" : [
    {
        "_t" : "NumberConfigurationElement", 
        "AsciiConfigNumber" : NumberInt(10), 
        "DataType" : NumberInt(1), 
        "ByteOffset" : NumberInt(0), 
        "Name" : "alcohol_limit", 
        "Description" : "The alcohol limit of the device (ug/l)", 
        "AckResponse" : "HT-CONFG,010,00119", 
        "DevicePart" : NumberInt(1), 
        "Value" : NumberInt(119), 
        "DefaultValue" : NumberInt(119), 
        "Min" : NumberInt(50), 
        "Max" : NumberInt(500)
    }, .....

dyouberg · Accepted Answer · 2016-12-08 17:45:00Z

2

You can do it like this(if your collection is called 'coll'):

db.coll.find().forEach(function(e) {
    var t = e.Elements;
    t.forEach(function(e) {
        e.isReadOnly=false
    });
    db.coll.update({ _id : e._id }, { $set: { Elements : t } } );
})

edited Dec 8, 2016 at 17:45

dyouberg

2,3521 gold badge15 silver badges22 bronze badges

answered Dec 8, 2016 at 16:36

guymaor86

4667 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

dyouberg Over a year ago

This pushes an additional document of { isReadOnly: false } to the existing elements array, not to each document inside the array. There is an open issue on the MongoDB JIRA about this, I think the only way to do this is inside JavaScript using Mongoose or another MongoDB driver.

Sede Over a year ago

@dyouberg there is better way to do this and you probably don't want to iterate the cursor like that as shown in the answer because there is a possibility for race condition and remember Murphy's law

dyouberg · Accepted Answer · 2016-12-08 17:31:40Z

0

@Styvane , this is what I came up with, it still seems a bit hacky.

var query = {
    Elements: {
        $elemMatch: {
            _t: { $exists: true },
            isReadOnly: { $exists: false }
        }
    }
};

while (db.collection.find(query).count() > 0) {
    db.collection.update(
        query, 
        { $set: { "Elements.$.isReadOnly": true } }
    );    
}

answered Dec 8, 2016 at 17:31

dyouberg

2,3521 gold badge15 silver badges22 bronze badges

1 Comment

Sede Over a year ago

This also is not good. This is factually correct in MongoDB 2.4 and even then, you can just iterate the cursor but instead a snapshot of the curor. The best way to do this is with bulk operation

tobsob · Accepted Answer · 2019-12-20 15:45:46Z

0

@David I've working solution with MongoDB 3.6+.

db.collection.update({},
    { $set: { "Elements.$[].isReadOnly": false } }, { multi: true }
)

This command will add isReadOnly = false field in all Element array field of documents.

The $position modifier specifies the location in the array at which the $push operator inserts elements. Without the $position modifier, the $push operator inserts elements to the end of the array. See $push modifiers for more information.

More details you can find on position operator docs

edited Dec 20, 2019 at 15:45

tobsob

6029 silver badges22 bronze badges

answered Dec 20, 2019 at 13:10

Saeed Khan

33 bronze badges

Collectives™ on Stack Overflow

Add new field to an Array of type object to a collection in MongoDB

3 Answers 3

2 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related