[SERVER-78468] Single interval query keysExamined information is inaccurate Created: 27/Jun/23 Updated: 27/Oct/23 Resolved: 11/Jul/23 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | 5.0.14 |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Chao Yin | Assignee: | Backlog - Query Execution |
| Resolution: | Works as Designed | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Assigned Teams: |
Query Execution
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| Operating System: | ALL | |||||||||||||
| Steps To Reproduce: | Create a replica set.
The above two queries should scan 2 documents: {a:1} and {a: ""} But the single interval query will only show keysExamined as 1.
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| Participants: |
| Description |
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When using a single interval query, the number of scanned keys displayed by explain is inaccurate. If the traversed data no longer meets the requirements , and the returned kv is empty code. keysExamined will not increase. code But multi-range queries use other methods to check bounds code keysExamined data can be counted correctly.
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| Comments |
| Comment by Chao Yin [ 19/Jul/23 ] |
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Thank you for your reply! |
| Comment by Kyle Suarez [ 11/Jul/23 ] |
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This is not a bug and known behavior: see for example this test. In the classic engine, we expect to scan more keys, but starting in v6.3, this query will use the new slot-based execution engine and scan a different amount. Note that a different number of keys examined is an implementation detail of the execution engine and not indicative of a bug. |