Details
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Type:
Improvement
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Status: Closed
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Priority:
Major - P3
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Resolution: Duplicate
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Affects Version/s: None
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Fix Version/s: None
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Component/s: Concurrency, Querying
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Labels:
Description
Current behavior of count is to construct a ClientCursor and perform non in mem yielding only after an elapsed tracker has elapsed. But this means it may hold a read lock while initial candidate documents are paged in.
if ( !ccPointer ) {
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if ( timeToStartYielding.intervalHasElapsed() ) {
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// Lazily construct a ClientCursor, avoiding a performance regression when scanning a very
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// small number of documents.
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ccPointer.reset( new ClientCursor( QueryOption_NoCursorTimeout, cursor, ns ) );
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}
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}
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else if ( !ccPointer->yieldSometimes( simpleEqualityMatch ? ClientCursor::DontNeed : ClientCursor::MaybeCovered ) ||
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!cursor->ok() ) {
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break;
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}
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In 2.0 count did not have non in mem yielding, so current behavior does improve on that.
Attachments
Issue Links
- related to
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SERVER-8579 Consolidate Mongod Lock/Resource Scheduling Logic
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- Closed
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