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Type:
Improvement
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Resolution: Unresolved
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: Aggregation Framework
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Query Optimization
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Query 2019-07-29
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(copied to CRM)
A very common use of an aggregation is to count elements by group:
db.items.aggregate([ {$group: {_id: "$category", count: {$sum: 1}}}])
If there is an index over category, this pipeline could be covered and no document retrieval is necessary.
Since this is a quite common pattern, you may take it into account and make use of indexes.
- is related to
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- Backlog
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- Closed
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- related to
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SERVER-69257 COUNT_SCAN plan not selected when unfiltered $group + $sum on _id performed
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- Needs Scheduling
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- Backlog
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