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?

Avinash
– Avinash

2016-02-01 10:45:24 +00:00
Commented Feb 1, 2016 at 10:45 — Avinash
– Avinash, Commented Feb 1, 2016 at 10:45

Alex Blex · Accepted Answer · 2016-02-02 10:42:51Z

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 2, 2016 at 10:42

answered Feb 1, 2016 at 11:15

Alex Blex

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Comments

chridam · Accepted Answer · 2016-02-01 11:01:18Z

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 1, 2016 at 11:01

chridam

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2 Comments

Azad Over a year ago

this my remove elements if that object does not have 'element' property

chridam Over a year ago

@Azzi That's why I said explicitly given that the embedded document has the element property only

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