Using $group to count all documents in the collection and getting back all entire documents by fieldName

Working with Data
1

Hello everyone,
I have a dataset like below:
{ “_id” :{ “time” : “01:00”}, “subDocument” : { “field1” : 42, “field2” : 10, “field3” : “yes” } }
{ “_id” :{ “time” : “01:01”}, “subDocument” : { “field1” : 14, “field2” : 6, “field3” : “yes”} }
{ “_id” :{ “time” : “01:02”}, “subDocument” : { “field1” : 6, “field2” : 11, “field3” : “yes” } }
{ “_id” :{ “time” : “01:03”}, “subDocument” : { “field1” : 3, “field2” : 26, “field3” : “no” } }

I want to count the the number of field3:"yes", but also want to show all entire fields.

 Result would look like below:
{
  "_id" : "yes",
  "agree" :
     [
       { "_id" :{ "time" : "01:00"}, "subDocument" : { "field1" : 42, "field2" : 10, "field3" : "yes"  }  }
       { "_id" :{ "time" : "01:01"}, "subDocument" : { "field1" : 14, "field2" : 6, "field3" : "yes"}  }
       { "_id" :{ "time" : "01:02"}, "subDocument" : { "field1" : 6, "field2" : 11, "field3" : "yes" }  }
     ],
   "totalYes" : 3
}

I tried to follow the example
https://docs.mongodb.com/manual/reference/operator/aggregation/group/#std-label-null-example
but I got an error.
How can I count the subDocument?

Many thanks
1 Like
2

It would help if you share the error you got and the exact query you tried. Most likely you have some cut-n-paste or syntax error. Without the exact query and without the exact error message there is nothing we can do except sending you to the same documentation you shared.

4

Hello Steeve, thanks for your reply. Here is the photo shows the original data.
image

I actually want to get the data length of all documents. In this case, would be 52.
I want to use this value for the for loop afterward.

here is my exact code:
// i create NoOfDoc and DLength just for counting the total no. of documents.
{
“$addFields”: { signals: { “NoOfDoc”:1} }
},

{
“$addFields”: { signals: { “DLength”:“length”} }
},

{
$group : {

  "signals" : { "DLength" : "length", iloop: {"$push": "$ROOT"}}

},
{
“$addFields”: { signals: { totalNoOfDoc: {"$sum":"$iloop.NoOfDoc"} }
}

5

the error message is:

image
image1118×117 10.4 KB

6

Looks like you are missing a closing brace in the above