CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
TheJediCowboy
TheJediCowboy

Reputation: 9222

Mongo aggregation $filter on true/false is not working

I have the following data

{  
   "_id":"57b5271231a5a203f8815e78",
   "name":"Group A",
   "created":new Date(1471489810155),
   "active":true,
   "invites":[  

   ],
   "requests":[  
      {  
         "_id":"57b683e531a5a21679b78e6c",
         "created":new Date(1471579109215),
         "user_id":"57b4c5f0291ebb23110b888e",
         "description":"Request From John",
         "active":true,
         "date":         new Date("2016-08-23T13:58:15-0700         "), 
            "         denied_users":[  

         ]
      },
      {  
         "_id":"57b683e531a5a21679a78e6c",
         "created":new Date(1471579109215),
         "user_id":"57b4c5f0291ebb13110b888e",
         "description":"Request A",
         "active":true,
         "date":         new Date("2016-08-23T13:58:15-0700         "), 
            "         denied_users":[  

         ]
      },
      {  
         "_id":"57b6841231a5a21679a78e6d",
         "created":new Date(1471579154271),
         "user_id":"57b4c5f0291ebb13110b888e",
         "description":"Request B",
         "active":true,
         "date":         new Date("2016-08-26T13:59:07-0700         "), 
            "         denied_users":[  

         ]
      }
   ],
   "fulfillments":[  

   ]
}

And am running the following query to Retrieve all embedded Request objects that have active = true. Nothing is being returned though.

db.groups.aggregate(
  [
    { $project : { "requests" : 1 }},
    { $unwind : "$requests" },
    { $project: {
        "requests": {
           "$filter": {
              "input": "$requests",
              "as": "item",
              "cond": { $eq: [ "$$item.active",true ] }
          }
        }
      }
    }
  ]
)

What am I doing wrong?

UPDATE

Would it be easier(the same) if I did the following

[
     { $project : { "requests" : 1 }},
     { $unwind : "$requests" }, 
     { $match : { "requests.active" : true } }
]

Upvotes: 0

Views: 2272

Answers (1)

JohnnyHK
JohnnyHK

Reputation: 311895

You just need to remove the $unwind stage from your pipeline:

db.groups.aggregate(
  [
    { $project: {
        "requests": {
           "$filter": {
              "input": "$requests",
              "as": "item",
              "cond": { $eq: [ "$$item.active",true ] }
          }
        }
      }
    }
  ]
)

Otherwise the $unwind changes the requests field from an array into a single object as it duplicates the docs which can't be used with $filter.

Upvotes: 3

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