MongoDb aggregate addField if an array of object contains object with specific attribute

Question

I need to add a completed attribute using addField aggregate query, if the orders array inside a collection (sales) contains an object with status attribute having value delivered.

db.sales.insertMany([
    {
        "_id" : 1,
        "salesId" : "2938432",
        "customerId" : "987677789",
        "amount:"23000"
        "orders":[{
            orderId:"TX8383428979382",
            status:"cancelled"
        },
        {
            orderId:"TX8383428979383",
            status:"fullfilled"
        }]
    },
    {
        "_id" : 1,
        "salesId" : "2938433",
        "customerId" : "987676578",
        "amount:"13000"
        "orders":[
        {
            orderId:"TX838342892437363",
            status:"placed"
        }]
    },
    .........
)]

My aggregate query

db.sales.aggregate([
  {$match:{....}},
  {$addFields:{
    completed: {
                 $cond: { if: { /* code to check if orders array contains an object with `status:fullfilled` }, then: true, else: false }
               }
  }},
])

How can I check for a match for an attribute inside array of objects.?

You can use the $map aggregation operator with the $addFields stage. $map will let you iterate over the orders array and you can check each element of the array for the condition and add a new attribute when there is match. — prasad_
– prasad_, Commented Apr 21, 2020 at 8:27
Thanks @prasad_. Seems like i can $reduce also. But I am unable to put it to code. Would be really helpful if u can put an example — Johnson Cherian
– Johnson Cherian, Commented Apr 21, 2020 at 10:30
Where do you want to add the completed attribute? For the "orders" sub-document or the root/top level? — prasad_
– prasad_, Commented Apr 21, 2020 at 10:46

prasad_ · Accepted Answer · 2020-04-21 11:00:29Z

2

Here is the aggregation which uses the $reduce array operator to add a new attribute completed which is derived based upon the orders.status "delivered".

db.sales.aggregate( [
{
    $addFields: {
        completed: {
            $reduce: {
                input: "$orders", initialValue: false,
                in: {
                     $cond: [ { $eq: [ "$$this.status", "delivered" ] }, 
                                true, 
                                "$$value"
                     ]
                }
            }
        }
    }
}
] ).pretty()

answered Apr 21, 2020 at 11:00

prasad_

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