mongoDB: remove empty objects in an object-array

Question

Unfortunately I got some false objects in an array in some documents, which are structured like this:

{
    "_id" : "8vJY4baMbdYkgHian",
    "title" : "Cars",
    "tradename" : [
        {

        },
        {
            "element" : "Audi"
        },
        {
            "element" : "Mercedes"
        }
    ]
}

As you can see in this example, the first object in the array is empty. How can I remove empty objects in all tradename-arrays of all documents in the collection?

Collection.update(
    { 'tradename': {} },
    { $pull: { 'tradename.$': '' } }
);

Possible duplicate of [Is object empty?](http://stackoverflow.com/questions/4994201/is-object-empty) — Avinash, Feb 01 '16 at 10:45

Alex Blex · Answer 1 · 2016-02-02T10:42:51.087

6

An alternative approach to remove empty objects from an array with no assumptions:

db.a.update(
    {"tradename": {}},
    { $pull: { 'tradename': {$in:[{}]} } },
    { "multi": true }
);

edited Feb 02 '16 at 10:42

answered Feb 01 '16 at 11:15

Alex Blex

34,704
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score 1 · Accepted Answer · answered Feb 01 '16 at 11:01

1

The following update operation using $pull updates all documents in the collection to remove empty objects from the array tradename, given that the embedded document has the element property only:

db.collection.update(
    { },
    { "$pull": { "tradename": { "element": { "$exists": false } } } },
    { "multi": true }
)

answered Feb 01 '16 at 11:01

chridam

100,957
23
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this my remove elements if that object does not have 'element' property – Azad Feb 01 '16 at 11:24
@Azzi That's why I said explicitly _given that the embedded document has the element property only_ – chridam Feb 01 '16 at 11:25

mongoDB: remove empty objects in an object-array

2 Answers2