How to find fields having array data type in mongodb? [duplicate]

Question

My requirement is to find number of records having arrays in field c. My document data looks like :

{ "_id" : ObjectId("5600c13c42e8973b2f4c0f36"), "a" : 4000, "b" : 2240, "c"  : 2140 }
{ "_id" : ObjectId("5600c40642e8973b2f4c0f37"), "a" : 4000, "b" : 42240, "c" : 2140 }
{ "_id" : ObjectId("5600c40942e8973b2f4c0f38"), "a" : 4000, "b" : 422240, "c" : 2140 }
{ "_id" : ObjectId("5600c44242e8973b2f4c0f39"), "a" : 4000, "b" : 422240, "c" : 2140 }
{ "_id" : ObjectId("56705c8cdaa8726c495fbdd9"), "d" : "f", "a" : "amm" }
{ "_id" : ObjectId("56705c97daa8726c495fbdda"), "d" : "qf" }
{ "_id" : ObjectId("5670b481a39d0dd706ec9a3c"), "a" : 21, "d" : 9 }
{ "_id" : ObjectId("56724f8e3e075703065e3988"), "a" : 3, "b" : 5, "c" : ["m", "n", 3 ] }   
{ "_id" : ObjectId("56724f983e075703065e3989"), "a" : 3, "b" : 5, "c" :  ["m", "n", "3" ] }

Expected output is 2.

I tried

db.fun.find({c:{$type:4}}).count()

I am not getting any values. Thanks.

Sarath Nair · Accepted Answer · 2015-12-17 06:46:14Z

2

Based on your input collection, you can use query like below:

db.fun.find({'c.0':{$exists:true}}).count()

Beware that if your collection has document of form

{"a" : 4000, "b" : 2240, "c": {"0": 222, "1", 333}}

the query fails as it retrieves this document as well.

For correct working in all cases you must use query of the following form:

db.fun.find({ $where : "Array.isArray(this.c)" }).count()

The problem using above query is that, queries using $where requires complete collection scan and uses server side JavaScript. Make sure you don't disable server side JavaScript if you are planning to use this.

Ref: https://docs.mongodb.org/v3.0/reference/operator/query/type/#querying-by-data-type

edited Dec 17, 2015 at 6:46

answered Dec 17, 2015 at 6:37

Sarath Nair

2,8682 gold badges24 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Madan Over a year ago

Thanks Sarath. isArray function is very new to me and gives desired output. So $typecode = 4 will not be useful to fetch array datatypes as we use typecode =2 for stings?

Sarath Nair Over a year ago

As the description goes typecode=2 will list all documents that is either a string or an array holding at least one string.

Collectives™ on Stack Overflow

How to find fields having array data type in mongodb? [duplicate]

1 Answer 1

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Linked

Related