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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: 2.6.3
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Component/s: Aggregation Framework
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Labels:
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Fully Compatible
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ALL
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Quint Iteration 3
Original title: Empty match at the start of the aggregation pipeline greatly impacts performance in 2.6, does not in 2.4
Aggregation below:
2.4.9 - 15-17 seconds
2.6.3 - 71-78 seconds
Removing the empty match:
2.4.9 - 15-17 seconds
2.6.3 - 15-16 seconds
db.collection.aggregate(
{ "$match" : { } },
{ "$project" : {
"doc.field" : 1 ,
"doc.doc1.doc2.field" : 1 ,
"_id" : 1
}
},
{ "$unwind" : "$doc" } ,
{ "$unwind" : "$doc.doc1"} ,
{ "$unwind" : "$doc.doc1.doc2"} ,
{ "$group" : {
"_id" : {
"doc+doc1+doc2+field" : "$doc.doc1.doc2.field"
} ,
"count#_id" : { "$addToSet" : "$_id" } ,
"count#variations+variationId" : { "$sum" : 1 }
}
}
);