How to write find query to get duplicate data from Arrays

[Nagamuni Reddy]

inpur Array:

 

{
  "_id" : ObjectId("5176b844ad366e8c93f96d85"),
  "userInfo" : [{
        "userId" : "100",,

        "empid" : "2002"  

     },

   {
      "userId" : "200",
      "empid" : "404"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }, {
      "userId" : "2002",
      "empid" : "4000"
    }, {
      "userId" : "2003",
      "empid" : "4000"
    }]
}

 

i have written query :     db.collection.find({ "userInfo.userId" : "200" }, { "userInfo.$" : 1 });

in the input array four records are having userId" : "200".but it is return only one record  like

 

{
  "_id" : ObjectId("5176b844ad366e8c93f96d85"),
  "userInfo" : [{
      "userId" : "200",
      "empid" : "404"
         "empid" : "4000"
    }]
}

 

But i want to display all records(whose userId" : "200")  from  array like below.

 

{
  "_id" : ObjectId("5176b844ad366e8c93f96d85"),
  "userInfo" : [{
        "userId" : "200",
      "empid" : "404"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }, {
      "userId" : "200",
      "empid" : "4000"
    }]
}

 

 

please send the query for this one.

 

Thanks and Regards,

N.NagaMuniReddy.

 

 

[Asya Kamsky]

There is no way to do this with a simple find.  You can write an aggregation framework pipeline to get back what you want or you can consider structuring your schema differently if you require getting this data via a find statement.

[Nagamuni Reddy]

Please send query how to write an aggregation framework pipeline for that.

 

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[masiegelmtr]

Hint: You'll probably want an $unwind operation to separate the userInfo array into one document per entry in the array.  Then, you can do a $match on the userId.

(http://docs.mongodb.org/manual/core/aggregation/)

[Gary R]

Perhaps an aggregation pipeline something like this:
db.collection.aggregate({$unwind:'$userInfo'}, {$match:{ 'userInfo.userId':'200'}}, {$group:{_id:'$_id',userInfo:{$push:'$userInfo'}}})

Certainly, only you know if it's worth going through the entire collection, or if a large number of docs could be eliminated with a $match at the beginning.

[Nagamuni Reddy]

Thanks a lot Gary.It is working fine.