Mongo DB第一个groupby计数无法显示

Question

[
 { "$match": {  
     "created":{  
         "$gte": ISODate("2015-07-19T07:26:49.045Z")
     },
     "created":{  
         "$lte": ISODate("2015-07-20T07:37:56.045Z")
     }
 }},
 { "$group:{  
     "_id":{  
         "ln":"$l.ln",
         "cid":"$cid"
     },
     "appCount":{ "$sum": 1 }
 }},
 {  "$group": {  
     "_id": {  "ln":"$_id.ln" },
     "cusappCount": {  "$sum": 1 }
 }},
 {  "$sort":{ "_id.ln":1  } }
]

In above mongo db query I am not able to display the appcount in result.. I am able to display cusappCount. Could anyone please help me on this

Answer 1

The $match is wrong to start with and does not do what you think. It is only selecting the "second" statement:

"created":{  
    "$lte": ISODate("2015-07-20T07:37:56.045Z")
 }

So your selections are incorrect to start with.

That and other corrections below:

[
    { "$match": {  
         "created": {  
             "$gte": ISODate("2015-07-19T07:26:49.045Z"),
             "$lte": ISODate("2015-07-20T07:37:56.045Z")
         }
     }},
     { "$group":{   
         "_id": {  
             "ln":"$l.ln",
             "cid":"$cid"
         },
         "appCount":{ "$sum": 1 }
     }},
     { "$group": {  
         "_id": "$_id.ln",
          "cusappCount": { "$sum": "$appCount" },
          "distinctCustCount": { "$sum": 1 }
     }},
     {  "$sort":{ "_id": 1  } }
]

Which seems to be what you are trying to do.

So your earier "count" is then passed to $sum when grouping at a "broader" level. The "second" count is just for the "distinct" items in the earlier key.

If you are trying to "retain" the values of "appCount", then the problem here is that your "grouping" is "taking away" the detail level that appears at. So for what it is woth, then this is where you use "arrays" in an output structure:

[
    { "$match": {  
         "created": {  
             "$gte": ISODate("2015-07-19T07:26:49.045Z"),
             "$lte": ISODate("2015-07-20T07:37:56.045Z")
         }
     }},
     { "$group":{   
         "_id": {  
             "ln":"$l.ln",
             "cid":"$cid"
         },
         "appCount":{ "$sum": 1 }
     }},
     { "$group": {  
         "_id": "$_id.ln",
          "cusappCount": { "$sum": 1 },
          "custs": { "$push": {
              "cid": "$_id.cid", "appCount": "$appCount" 
          }}
     }},
     {  "$sort":{ "_id": 1  } }
]