[SERVER-83196] SBE multiplanning may chooses the wrong plan Created: 13/Nov/23 Updated: 30/Nov/23 |
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| Status: | Open |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Xiaochen Wu | Assignee: | Backlog - Query Optimization |
| Resolution: | Unresolved | Votes: | 1 |
| Labels: | query-director-triage | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Assigned Teams: |
Query Optimization
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| Operating System: | ALL | ||||||||||||||||
| Participants: | |||||||||||||||||
| Description |
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For SBE, we implemented a default limit of 10,000 reads for each candidate plan. This bounds the expense of the trial period cost at 10,000n where n is the number of plans – an important backstop given that we may incidentally trial the “wrong” plan(s) first. However, this limit can be much higher for the Classic multi-planner. As a result, the SBE multi-planner will sometimes do less partial execution than the Classic multi-planner, rendering it unable to distinguish amongst plans when no well-indexed plan exists. |