how to count number of sub object (same document) in mongodb [duplicate]

Question

Example document:

{
    "aliases" : {
        "name" : [ 
            "Brinton McKay", 
            "Dr. Theopolis", 
            "Galactic Spiral Sound", 
            "Highrise", 
            "Memory Boy", 
            "Semblance Factor", 
            "Spy (2)", 
            "Three O'Clock High"]}
}

How i can count the number of "name" under "aliases"? I would like to print all _id who which contains more than 3 aliases. any help would be appreciated.

So in this case it would be: db.coll.find({'aliases.name.3': {$exists: true}}) — JohnnyHK
– JohnnyHK, Commented Jun 11, 2015 at 12:30

Yathish Manjunath · Accepted Answer · 2015-06-11 12:27:46Z

0

Please check the below query :

db.collection.find({ $where : function() 
{ return Object.keys(this.aliases.name).length > 3 } });

OR

db.collection.aggregate([
{$project : { _id :1 , numb : {$size : "$aliases.name"} }
},
{$match : { numb :{$gt : 3 }}
}
]);

PS : you can see the documentation in below link : http://docs.mongodb.org/manual/reference/operator/query/where/

edited Jun 11, 2015 at 12:27

answered Jun 11, 2015 at 4:22

Yathish Manjunath

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5 Comments

mrana Over a year ago

This is the error: error: { "$err" : "Can't canonicalize query: BadValue $size needs a number", "code" : 17287 }

Yathish Manjunath Over a year ago

can you check the above query ?

mrana Over a year ago

It works but as { $size: 3 } not as {$size:{$gt:3}} , how i can use $gt? Thanks very much

Yathish Manjunath Over a year ago

I have posted anothet query using aggregate function, can you check that as well. I have edited that in my post. please try them.

mrana Over a year ago

This one is perfect: db.coll.find({'aliases.name.3': {$exists: true}}) Great JohnnyHK & also Yathish. You guys are good.

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