Find if an element in array has value equal to parent element value

Question

Let's say we have a collection of documents like this one:

{
    "_id" : ObjectId("591c54faf1c1f419a830b9cf"),
    "fingerprint" : "3121733676",
    "screewidth" : "1920",
    "carts" : [ 
        {
            "cartid" : 391796,
            "status" : "New",
            "cart_created" : ISODate("2017-05-17T13:50:37.388Z"),
            "closed" : false,
            "items" : [ 
                {
                    "brandid" : "PIR",
                    "cai" : "2259700"
                }
            ],
            "updatedon" : ISODate("2017-05-17T13:51:24.252Z")
        }, 
        {
            "cartid" : 422907,
            "status" : "New",
            "cart_created" : ISODate("2017-10-23T08:57:06.846Z"),
            "closed" : false,
            "items" : [ 
                {
                    "brandid" : "PIR",
                    "cai" : "IrHlNdGtLfBoTlKsJaRySnM195U"
                }
            ],
            "updatedon" : ISODate("2017-10-23T09:46:08.579Z")
        }
    ],
    "createdon" : ISODate("2016-11-08T10:29:55.120Z"),
    "updatedon" : ISODate("2017-10-23T09:46:29.486Z")
}

How do you extract only the documents where no item in the array $.carts have $.carts.closed set to true and $.carts.updatedon greater than $.updatedon minus 3 days ?

I know how to do find all the documents where no item in the array satisfy the condition $and: [closed: {$eq: true}, {updatedon: {$gt : new ISODate("2017-10-20T20:15:31Z")}}]

But how can you reference the parent element $.updatedon for the comparison?

In plain mongodb shell query language it would aleady be of help.

But I am actually accessing it using c# driver, so my query filter is like this:

FilterDefinition<_visitorData> filter;
filter = Builders<_visitorData>.Filter
  .Gte(f => f.updatedon, DateTime.Now.AddDays(-15));
filter = filter & (
  Builders<_visitorData>.Filter
    .Exists(f => f.carts, false) 
      | !Builders<_visitorData>.Filter.ElemMatch(f => 
        f.carts, c => c.closed && c.updatedon > DateTime.Now.AddDays(-15)
      )
);

How can I replace DateTime.Now.AddDays(-15) with a reference to the document root element updatedon?

Answer 1

You can project the difference of carts.updatedon and updatedon and then filter out the results from this aggregation pipeline.

coll.aggregate([{'$unwind':'$carts'},
                {'$match':{'closed':{'$ne':true}}},
                {'$project':{'carts.cartid':1,'carts.status':1,'carts.cart_created':1,'carts.closed':1,'carts.items':1,'carts.updatedon':1,'updatedon':1,'diff':{'$subtract':['$carts.updatedon','$createdon']}}},
                {'$match': {'diff': {'$gte': 1000 * 60 * 60 * 24 * days}}}])

days = 3 will filter out results more than 3 days difference documents.

I have just given the example of how you can use $subtract to find date difference and filter documents based on that.

Answer 2

well I was in a similar situation few days back. I tackled it by using Jobject of Newtonsoft.Json. Create a function to return bool which actually process each document take it as input.

  Jobject jOb=Jobject.parse(<Your document string>);
  JArray jAr=JArray.Parse(jOb["carts"]);
  If(jOb["updateon"]=<Your Business Validation>)
  {
     foreach(var item in jAr)
       if(item["closed"]==<Your validation>){ return true}         

   }
 return false;

I hope this helps :) If you handling with any null values in those properties then please use Tryparse and out variable.