[SERVER-56480] allPlansExecution array shows extraneous execution stats when multi-planning did not occur Created: 29/Apr/21 Updated: 29/Oct/23 Resolved: 26/May/21 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | 5.0.0-rc0, 5.1.0-rc0 |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | David Storch | Assignee: | Irina Yatsenko (Inactive) |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | neweng, post-rc0, sbe-post-rc0 | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Backwards Compatibility: | Fully Compatible | ||||
| Operating System: | ALL | ||||
| Backport Requested: |
v5.0
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| Sprint: | Query Execution 2021-05-31 | ||||
| Participants: | |||||
| Description |
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This is a regression in 5.0 and does not affect previous verisons. In 4.4 and all previous versions, the allPlansExecution section is empty when there is just one candidate plan. As a simple example, consider this query which has only a collection scan plan:
The rationale for this behavior is that the allPlansExecution section displays information about the multi-planning trial period. It can help you diagnose why one plan is chosen over another. However, if there is just one plan, then there is no trial execution period, and therefore the allPlansExecution information describing this trial period should be omitted. In the master branch, we have introduced a regression where a query with just a single candidate plan displays duplicate information about that plan in the allPlansExecution section:
This explain was generated from the classic execution engine, but the same problem exists when SBE is enabled. Furthermore, I suspect that the issue was introduced in development of the SBE project, since supporting explain for SBE required some surgery to the explain code. |
| Comments |
| Comment by Vivian Ge (Inactive) [ 06/Oct/21 ] |
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Updating the fixversion since branching activities occurred yesterday. This ticket will be in rc0 when it’s been triggered. For more active release information, please keep an eye on #server-release. Thank you! |
| Comment by Githook User [ 26/May/21 ] |
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Author: {'name': 'Irina Yatsenko', 'email': 'irina.yatsenko@mongodb.com', 'username': 'IrinaYatsenko'}Message: (cherry picked from commit cb26584ed0dcbf5c3736c01bd7fb2636babed312) |
| Comment by Irina Yatsenko (Inactive) [ 26/May/21 ] |
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Even though the change affects `explain` output, it brings it back to the prior released behaviour (the fix will be ported to 5.0 as well) so no downstream notice needed. |
| Comment by Githook User [ 26/May/21 ] |
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Author: {'name': 'Irina Yatsenko', 'email': 'irina.yatsenko@mongodb.com', 'username': 'IrinaYatsenko'}Message: |