MongoDB push into nested array without using indices

Question

I'm looking to $push something into a nested array, of which the parent array matches a simple property condition:

Here's how my document looks:

{
  name: "Foo",
  boardBucket: {
    currentBoardId: 1234,
    items: [ <- looking to push into `boardItems` of an `item` in this Array
      { 
        boardId: 1234, <- that has `boardId: 1234` 
        boardItems: [ "barItem", "deyItem" ] <- Final Array I want to push to
      }
    ]
  }
}

So I'd like to push "fooItem" in boardItems of item that has boardId: 1234

Option 1: I can use dot notation and access by index

I can certainly do a $push by using dot.notation which uses the index of the item like so:

this.update({ '$push': {"boardBucket.items.0.boardItems": "fooItem" } });

But what if I don't know the index?

How can I push into boardItems of item with boardId: 1234 without using the indices (using the boardId instead)?

Note:

I'm using mongoose as the db driver
I'd like to avoid using mongoose's save() cause it tends to be buggy + it seems to keep a copy of the object locally which i'd like to avoid
Just direct update() mongo queries are what I'm after
I'd certainly like to avoid any type of whole-document fetching to perform this update as my documents are huge in size

@CetinBasoz thanks - It's not clear from the docs how that would work in this case - can you add a minimal example as an answer? — nicholaswmin
– nicholaswmin, Commented Aug 19, 2016 at 9:46

Filip Lauc · Accepted Answer · 2016-08-19 13:58:33Z

3

I think this should do the trick:

this.update(
  {"boardBucket.items": {$elemMatch: { boardId: "1234"}}},
  {'$push': {"boardBucket.items.boardItems": "fooItem" }}
);

edited Aug 19, 2016 at 13:58

answered Aug 19, 2016 at 10:02

Filip Lauc

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6 Comments

Filip Lauc Over a year ago

@CetinBasoz answer is more precise. My approach would push in to every boardBucket items array that has the "boardId": "1234".

nicholaswmin Over a year ago

That's exactly what I want to do as well - for some reason it throws cannot use the part (items of boardBucket.items.boardId) to traverse the element

nicholaswmin Over a year ago

I think you're missing a curly bracket after {$elemMatch: { boardId: "1234"}}, , should be {$elemMatch: { boardId: "1234"}}},

nicholaswmin Over a year ago

hate to be a pest but it doesn't seem to work - Although the query (with my corrected } addition) runs and returns nModified : 1, it doesn't seem to add "fooItem" anywhere in the DB (checked the entire DB in case it get's erroneously added somewhere else) - Note that the boardId's definitely match so that's not the problem - any ideas?

Uğur Gümüşhan Over a year ago

I confirm that: {'$push': {"boardBucket.items.boardItems": "fooItem" }} works

|

Cetin Basoz · Accepted Answer · 2016-08-19 10:01:54Z

2

(Sorry for not sampling in the first place, was on a rush then)

db.myDb.insert({
  name: "Foo",
  boardBucket: {
  currentBoardId: 1234,
    items: [ 
      { 
        boardId: 1234, 
        boardItems: [ "barItem", "deyItem" ] 
      },
      { 
        boardId: 1235, 
        boardItems: [ "dontPushToThisOne" ] 
      }
    ]
  }
});

db.myDb.insert({
  name: "Foo2",
  boardBucket: {
    currentBoardId: 1236,
    items: [ 
      { 
        boardId: 1236, 
        boardItems: [ "dontPushToThisOne" ] 
      }
    ]
  }
});


db.myDb.update( 
   { "boardBucket.currentBoardId":1234,
     "boardBucket.items.boardId":1234},
   { "$push" : {"boardBucket.items.$.boardItems":"fooItem"} }, {multi:1} );

answered Aug 19, 2016 at 10:01

Cetin Basoz

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2 Comments

nicholaswmin Over a year ago

Awesome - Strangely enough I'm getting this error however:

cannot use the part (items of boardBucket.items.boardId) to traverse the element ({items: [ { boardId: "147813751944",", _id: ObjectId('57b6da3fb0fcf466044a4c20')} ]})

- Is it because items is an array?

Cetin Basoz Over a year ago

That may be mongoose specific, I don't use it. I wrote and tested the code in default mongo shell. (you use the quotes around it, right?)

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