how to update or insert many objects in an array subdocument in mongodb?

Question

the document model I'm using is as follows.

{
    "_id" : "a301c595-f6f3-4ede-91c5-f1cabd548338",
    "UserName" : "3@3.com",
    "Revision" : 6,
    "UserVocabs" : [
        {
            "Vocab" : "apple",
            "LearnStatus" : 0,
            "lastChanged" : 213232
        },
        {
            "Vocab" : "book",
            "LearnStatus" : 0,
            "lastChanged" : 213132
        },
    ]
}

I'm trying to add or replace objects in the UserVocabs array by their Vocab field so I don't know their indexes. till now the only solution I used is to first pull the object and then trying to push its updated version back in the array. but it needs 2 query for each object updates. is there any better solution out there?

armnotstrong · Answer 1 · 2017-08-05T07:29:06.287

1

You could update one of the elements of array by its index like

 db.test.update({"_id": "a301c595-f6f3-4ede-91c5-f1cabd548338"},{$set:{"UserVocabs.1.Vocab":"orange"}})

Or if you want to modify all the elements you could replace the 1 with $ which is a wildcard of an arbitrary index. (you may have to set the last two parameters tags to make this work though)

and could extends the array with

 db.test.update({"_id": "a301c595-f6f3-4ede-91c5-f1cabd548338"},{$addToSet:{"UserVocabs":{"key1":"value1","key2":"value2"}}})

Removable of elements could ref to this answer

If you want to use the value of array to find the elem to replace you could:

db.test.update({"UserVocabs.Vocab": "apple"},{$set:{"UserVocabs.$.Vocab":"orange"}})

edited Aug 05 '17 at 07:29

answered Aug 05 '17 at 07:10

armnotstrong

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the index I'm using is the vocab name ("Vocab" : "apple"). I'll update the question – alizx Aug 05 '17 at 07:15
@alizx check the edit – armnotstrong Aug 05 '17 at 07:29
the second approach adds if the object is different in at least one field. the only field that needed to be checked for me is vocab field – alizx Aug 05 '17 at 08:00

how to update or insert many objects in an array subdocument in mongodb?

1 Answers1