mongo count elements in array
> db.mycollection.insert({'foo':[1,2,3,4]})
> db.mycollection.insert({'foo':[5,6,7]})
> db.mycollection.aggregate([{$project: { count: { $size:"$foo" }}}])
{ "_id" : ObjectId("5314b5c360477752b449eedf"), "count" : 4 }
{ "_id" : ObjectId("5314b5c860477752b449eee0"), "count" : 3 }mongodb aggregate count
#return the number of documents whose "field" field has a value of A
query = db.collection.aggregate([{
"$match": {
"field": "A"
}
},{
"$count": "number of occurrences"
}])Copyright © 2021 Codeinu
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