[SERVER-12679] Regression of queries that project a large number of fields Created: 11/Feb/14 Updated: 06/Dec/22 Resolved: 22/Aug/19 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Performance, Querying |
| Affects Version/s: | 2.5.5 |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Davide Italiano | Assignee: | Backlog - Query Team (Inactive) |
| Resolution: | Won't Do | Votes: | 1 |
| Labels: | 26qa, Performance, query-44-grooming | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Attachments: |
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| Assigned Teams: |
Query
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| Operating System: | ALL |
| Steps To Reproduce: | Linux ip-10-0-0-85 3.11.0-12-generic #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux |
| Participants: |
| Description |
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Some of my benchmarks show the following (it happens both in the single and multi-threaded case scenario). When the number of fields to project is small the regression is not noticeable, I'll try to investigate a bit more on the root cause. Master (as per today)
2.4.9
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| Comments |
| Comment by Charlie Swanson [ 22/Aug/19 ] | ||||||||||||||||||||||||
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This is an old report of a performance regression that we do not plan on spending time investigating. | ||||||||||||||||||||||||
| Comment by Davide Italiano [ 19/Feb/14 ] | ||||||||||||||||||||||||
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I modified the script to change the number of fields that are projected (starting from 5, up to 500). | ||||||||||||||||||||||||
| Comment by Davide Italiano [ 11/Feb/14 ] | ||||||||||||||||||||||||
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I had time to do some profiling.
Major bottleneck is lookup in the StringMap (FieldMap)
Apparently this commit is responsible for the performance drop, reverting it I'm completely able to come back to the 2.4.9 numbers |