Querying array of objects in MongoDB using only find method

Question

Look the following documents in a contacts collection on MongoDB 3.4:

{
    "_id" : ObjectId("58f045526320ef24fc61fdb2"),
    "name" : "John Doe",
    "tags" : [
        {
            "name": "tagA", 
            "created_at": ISODate("2017-01-27T10:30:00Z")
        },
        {
            "name": "tagB", 
            "created_at": ISODate("2017-01-28T13:30:00Z")
        }
    ],
},
{
    "_id" : ObjectId("58f045526320ef24fc61fdb3"),
    "name" : "Johnny Doe",
    "tags" : [
        {
            "name": "tagA", 
            "created_at": ISODate("2016-12-21T19:30:00Z")
        },
        {
            "name": "tagC", 
            "created_at": ISODate("2017-01-28T13:30:00Z")
        }
    ],
}
.
. 
.

Is there any query using only find method (nor aggregate framework, nor $where) that can return:

The contacts who have all the following tags: [tagA, tagC]
The contacts who don't have all of these tags: [tagC, tagD]
The contacts with all tags in 2017

what you tried so far? and what is the error you are getting? — AshokGK
– AshokGK, Commented Apr 18, 2017 at 12:42
I just can't find a query to return the contacts that fulfill those conditions. Note that it is not the classic query that return for example contacts who have tagA or tagC. — Delmo
– Delmo, Commented Apr 18, 2017 at 12:51
Take a look at stackoverflow.com/questions/23595023/…. It has similar examples that do an "exact match" - meaning that those answers show how to find contact who have an exact set of tags. For example to answer question 1, db.collection.find({"tags": {"$not": {"$elemMatch": {"name": {"$nin": ["tagA", "tagC"]}}}}}) — Jeff J
– Jeff J, Commented Apr 18, 2017 at 14:12
Thanks @JeffJ I guess now I can write the three queries above using the key point you commented from the other stackoverflow post: apply $not over the complement of a subset. You can now go ahead to answer the question putting the query for every case so that I can accept the answer as the right one. — Delmo
– Delmo, Commented Apr 18, 2017 at 16:17
I really don't have good data to test. You can try something like db.collection.find({ "tags.name": { $all: [ "tagA" , "tagB" ], $nin: [ "tagC" , "tagD" ]},"tags.created_at":{$gte: ISODate("2017-01-01"),$lt:ISODate("2018-01-01")}}); — s7vr
– s7vr, Commented Apr 18, 2017 at 20:36

Community · Accepted Answer · 2017-05-23 11:54:33Z

2

I found a similar question at Check if every element in array matches condition.

To find the contacts who have all the following tags: [tagA, tagC], you can use a double negative to find the documents that do NOT have elements NOT in [tagA, tagC]

db.collection.find({"tags": {"$not": {"$elemMatch": {"name": {"$nin": ["tagA", "tagC"]}}}}})

To find the contacts who don't have all of these tags: [tagC, tagD]

db.collection.find({"tags": {"$elemMatch": {"name": {"$nin": ["tagC", "tagD"]}}}})

A similar query can be done for the date as well, although using $or

db.collection.find({"tags": {"$not": {"$elemMatch": {"$or": [ 
    {"createdAt": {"$lt": ISODate("2017-01-01T00:00:00.000Z")}},
    {"createdAt": {"$gt": ISODate("2017-12-31T23:59:59.999Z")}}]}}}})

edited May 23, 2017 at 11:54

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answered Apr 18, 2017 at 20:18

Jeff J

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1 Comment

Delmo Over a year ago

I voted up your answer but the @Veeram solution for the two first queries are the best, IMHO. Note that they are simpler, therefore more efficient. That is why I will accept his answer as the right one when he adds the answer officially. However, thanks for the good point about the negation of the complement which is the right answer for the third query (in my opinion).

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