Adding an element to a sub array of an array in MongoDB

Question

I want to create a mongodb document structure like below.

data:[[{a:b},{b:c}],[{e:f}],[{f:g},{j:h},{i:l}]]

This structure will allow me to add new sub array element, 4th one to the existing data array which contains three sub arrays in the above example, if required.

I am able to add new sub array element using below command from mongodb shell.

db.xyz.update({'id':'A01'},{$push:{data:[]}},{})

However, I am unable to findout solution for pushing data in to respective arrays. The following command is not working.

db.xyz.update({'id':'A01'},{$push:{data[0]:{$push:{a:b}}}},{})

felix · Accepted Answer · 2017-01-03 11:56:02Z

2

A single $push should be enough. Try this instead:

db.xyz.update({'id':'A01'}, {$push: {"data.0": {a: "b"}}})

result:

{
   "_id":ObjectId("586b907a4979a26deaacf4ad"),
   "data":[
      [
         {
            "a":"b"
         },
         {
            "b":"c"
         },
         {
            "a":"b"
         }
      ],
      [
         {
            "e":"f"
         }
      ],
      [
         {
            "f":"g"
         },
         {
            "j":"h"
         },
         {
            "i":"l"
         }
      ]
   ]
}

answered Jan 3, 2017 at 11:56

felix

9,3158 gold badges44 silver badges65 bronze badges

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

2 Comments

Satya Narayana Over a year ago

And for retrieving the first element of first array in data i am trying db.xyz.find({'id':'A01'},{data.0:{$slice:1}}) but unable to get it. i am getting all the array elements of first array while trying db.xyz.find({id:'A01'},{data:{$slice:1}}) how to get the first element of first array.

felix Over a year ago

@SatyaNarayana you can do this like this: db.xyz.aggregate([{$match: {_id: "A01"}}, {$project: {data: {$arrayElemAt: [{$arrayElemAt: ["$data", 0]}, 0]}}} ])

Collectives™ on Stack Overflow

Adding an element to a sub array of an array in MongoDB

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related