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Type:
New Feature
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Resolution: Duplicate
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Priority:
Minor - P4
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None
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Affects Version/s: None
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Component/s: Performance
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None
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Query Optimization
> db.coll1.insert({a:1, b:2})
...
> db.coll1.createIndex({a:1, b:1})
...
> db.coll1.explain().aggregate({$group: {_id: ["$a", "$b"]}})
... "inputStage" : { "stage" : "COLLSCAN" ...
The aggregation on a single key generates efficient DISTINCT_SCAN:
> db.coll1.explain().aggregate({$group: {_id: "$a"}})
... "inputStage" : { "stage" : "DISTINCT_SCAN", ...
- duplicates
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SERVER-53626 Minimize index scanning when retrieving distinct values grouped by more than one field
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- Backlog
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