Details
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Bug
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Resolution: Done
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Major - P3
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2.6.3
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Fully Compatible
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ALL
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Quint Iteration 3
Description
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(
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{ "$match" : { } },
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{ "$project" : {
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"doc.field" : 1 ,
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"doc.doc1.doc2.field" : 1 ,
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"_id" : 1
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}
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},
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{ "$unwind" : "$doc" } ,
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{ "$unwind" : "$doc.doc1"} ,
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{ "$unwind" : "$doc.doc1.doc2"} ,
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{ "$group" : {
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"_id" : {
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"doc+doc1+doc2+field" : "$doc.doc1.doc2.field"
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} ,
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"count#_id" : { "$addToSet" : "$_id" } ,
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"count#variations+variationId" : { "$sum" : 1 }
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}
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}
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);
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