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Type:
Improvement
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: Querying
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Query Execution
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(copied to CRM)
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0
Tested with WiredTiger which seems to exhibit this more than MMAP.
Covered index query which has to return all the documents from a collection is slower than just a full collection scan even in cases where index is quite small and collection is very large.
Looking at where we spend time, it appears for each "document" we need to "synthesize" from the index we allocate and free some memory. We apparently have some optimization for avoiding that in collection scan
but not full index scan. This is to track the same optimization for index scan.
- causes
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SERVER-59341 Query planner choses collscan over covered index scan for huge collection
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- Closed
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- is depended on by
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- Needs Scheduling
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- is duplicated by
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- Closed
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- is related to
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- Closed
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SERVER-98479 Revisit full covered index scans as collection scan alternative
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- Needs Scheduling
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- Closed
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