Details
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Question
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Status: Closed
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Major - P3
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Resolution: Gone away
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Description
We have a 'fast' count mode that runs in cases like a query on
{a:'c',b:'d'}with index
{a:1,b:1}. (Among other restrictions, all fields of the index must be present and the queried values must not be objects or numbers.) This optimization adds implementation complexity and has been a source of bugs (eg SERVER-4529). Additionally, the performance of this special counting mode has likely been degraded by changes over time (eg SERVER-3449).
Also, I'm not sure if we've actually measured the performance of fast count mode. We might consider removing it, otherwise we might refactor it out of the main query path.
Attachments
Issue Links
- is related to
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SERVER-4529 fast count mode should not be used when matching against null
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- Closed
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SERVER-1752 improve the performance of simple counts
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- Closed
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