Remove element from nested array mongodb

Question

i have the following document , it has two array\'s , one inside the other ,
attachment array and files array inside attachment array . i want to delete an element insi

Answer 1

You can try below update query in 3.6 version.

Invoice.update( 
 {}, 
 {"$pull":{"attachment.$[].files":{_id:ObjectId("5b7969ac8fb15f3e5c8e844e")}}}, 
 {"multi": true}, function (err, result) {console.log(result);
});

Use db.adminCommand( { setFeatureCompatibilityVersion: 3.6 or 4.0 depending on your version } ) if your are upgrading from old version.

Answer 2

For Mongodb version prior to 3.6

There is only one nested level here so you can simply use $ positional operator.

Invoice.update(
  { "attachment.files._id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") },
  { "$pull": { "attachment.$.files": { "_id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") }}},
  { "multi": true }
)

For Mongodb version 3.6 and above

If you want to update multiple elements inside attachement array then you can use $[] the all positional operator.

const mongoose = require("mongoose")

Invoice.update(
  { "attachment.files._id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") },
  { "$pull": { "attachment.$[].files": { "_id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") }}},
  { "multi": true }
)

And If you want to update single element inside the attachment array then you can use $[<identifier>] that identifies the array elements that match the arrayFilters conditions.

Suppose you want to update only an element inside attachment having _id equal to ObjectId(5b7934f54b2a961d081de9ab)

Invoice.update(
  { "attachment.files._id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") },
  { "$pull": { "attachment.$[item].files": { "_id": mongoose.Types.ObjectId("5b7937014b2a961d082de9bf") } } },
  { "arrayFilters": [{ "item._id": mongoose.Types.ObjectId("5b7934f54b2a961d081de9ab") }], "multi": true }
)