-
Type:
New Feature
-
Resolution: Duplicate
-
Priority:
Major - P3
-
None
-
Affects Version/s: None
-
Component/s: Aggregation Framework
-
Labels:None
We have operators $first and $last, these accumulation operators allow you to select the first or last entries for a given value within a group operator.
Can we add a $first-n and $last-n operator which would return several of the last values in an array as such:
Initial Data
for(i=0;i<100;i++){db.t2.insert({name :"one", x:i})} for(i=0;i<100;i++){db.t2.insert({name :"two", x:i})} for(i=0;i<100;i++){db.t2.insert({name :"three", x:i})}
Aggregation command example
db.t2.aggregate([{$group: {_id:"$name", x :{ "$last" :["$x", 3]}}}])
Example output
{ "_id" : "three", "x" : [ 99, 98, 97 ] }
{ "_id" : "two", "x" : [ 99, 98, 97 ] }
{ "_id" : "one", "x" : [ 99, 98, 97 ] }
- duplicates
-
SERVER-9377 Allow collecting "top" N values for each group
-
- Closed
-