Details
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Improvement
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Status: Blocked
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Major - P3
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Resolution: Unresolved
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4.1.7
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None
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Query Execution
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Query 2020-03-23
Description
This is a feature request to enhance the behaviour of the $sample aggregation command by adding to the plan optimizer the WiredTiger “readOnce: true” option for MongoDB cursors (SERVER-36068).
The intended purpose behind this enhancement is so $sample does not (or is less likely to) cache the result set. A sample by definition is unlikely to be used again by subsequent samples, thereby caching has no benefit and only serves to add unwanted cache pressure and workload contention.
Attachments
Issue Links
- depends on
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SERVER-47118 Investigate the behavior of read_once cursors
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- Backlog
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SERVER-47055 Investigate performance regression in initial sync collection scan with readOnce cursors
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- Closed
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SERVER-36068 Expose a user-accessible cursor option to avoid caching data from reads
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- Closed
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