Q33: How do you analyze query performance using .explain('executionStats')?
Executing .explain('executionStats') returns execution details for a query:
winningPlan: Selected execution path strategy.executionStages: Stage breakdown (IXSCANvsCOLLSCAN).- Key Metrics:
nReturned(matching documents),totalKeysExamined(indexed keys checked),totalDocsExamined(documents scanned). Target ratio:totalDocsExamined / nReturnedclose to 1.
Key Takeaways
- Analyzes query execution performance.
- Ideal ratio:
totalKeysExamined$approx$nReturned, withtotalDocsExaminedminimized.
Knowledge Check
In an explain plan output, what does totalDocsExamined = 10000 and nReturned = 5 indicate?