Cant find duplicate values for array part in mongodb

Question

db.school.find({ "merchant" : "cc8c0421-e7fc-464d-9e1d-37e168b216c3" })

this is an example document from school collection of that query:

    { 
        "_id" : ObjectId("57fafasf2323232323232f57682cd42"), 
        "status" : "wait", 
"merchant" : "cc8c0421-e7fc-464d-9e1d-37e168b216c3",
        "isValid" : false, 
    "fields" : { "schoolid" : {
            "value" : "2323232", 
            "detail" : {
                "revisedBy" : "teacher", 
                "revisionDate" : ISODate("2015-06-24T09:22:44.288+0000")
            }, 
            "history" : [

            ]
        }}
    }

I want to see which has duplcate schoolid. SO i do this:

db.school.aggregate([
{$match:{  "merchant" : "cc8c0421-e7fc-464d-9e1d-37e168b216c3"
  { $group: {
    _id: { fields.schoolid.value: "$fields.schoolid.value" },  
    count: { $sum: 1 } 
  } }, 
  { $match: { 
    count: { $gte: 2 } 
  } },
  { $sort : { count : -1} },
  { $limit : 10 }
]);

but it gives error.

a lot of errors for a lot of lines

i tried to do like this

_id: { "fields.schoolid.value": "$fields.schoolid.value" },

or _id: { 'fields.schoolid.value': "$'fields.schoolid.value'" },

but did not work. ow can i use it?

felix · Accepted Answer · 2017-04-04 12:13:46Z

1

According to the document you provided, there is no fields field, so the group stage can't work. Your query should be :

db.school.aggregate([
  { $match: {  "merchant" : "cc8c0421-e7fc-464d-9e1d-37e168b216c3"}},
  { $group: {
    _id: { value: "$fields.schoolid.value" },  
    count: { $sum: 1 } 
  } }, 
  { $match: { 
    count: { $gte: 2 } 
  } },
  { $sort : { count : -1} },
  { $limit : 10 }
]);

Also note that fields.schoolid.value is not a valid fieldname, you need to enclode it in "" or to remove the "."

edited Apr 4, 2017 at 12:13

answered Apr 4, 2017 at 9:35

felix

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1 Comment

mark Over a year ago

i added fields. sorry. i enclosed it in with "" but still same

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