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Type:
Question
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Resolution: Duplicate
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Priority:
Major - P3
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None
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Affects Version/s: 4.3.2
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Component/s: Aggregation Framework
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None
data = [
{"name": a, dept: "IT", score: 150},
{"name": b, dept: "IT", score: 100},
{"name": c, dept: "Sales", score: 260},
{"name": d, dept: "Sales", score: 200}
]
Now we run following aggregation
db.serviceoffering.aggregate([
{$sort: {score: 1}},
{$group: {_id: {dept: "$dept"}, user: {$push: "$$ROOT"}}}
])
Now after $sort pipeline the result would be following:
data = [
{"name": b, dept: "IT", score: 100},
{"name": a, dept: "IT", score: 150},
{"name": d, dept: "Sales", score: 200},
{"name": c, dept: "Sales", score: 260}
]
But after $group pipeline result becomes:
{
{
_id: IT,
user:[
{"name": d, dept: "Sales", score: 200},
{"name": c, dept: "Sales", score: 260}
]
},
{
_id: Sales,
user:
[
{"name": b, dept: "IT", score: 100},
{"name": a, dept: "IT", score: 150}
]
}
}
If you observe the result data has been taken from bottom and hence even after sort d,c are on top in the final result.
- duplicates
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SERVER-24799 $group aggregation command should maintain document order
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- Closed
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