[SERVER-13088] Scalability of distinct is sub-optimal Created: 07/Mar/14 Updated: 06/Dec/22 Resolved: 14/Sep/18 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Concurrency, MMAPv1, Querying |
| Affects Version/s: | 2.6.0-rc1 |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Davide Italiano | Assignee: | Backlog - Query Team (Inactive) |
| Resolution: | Won't Fix | Votes: | 2 |
| Labels: | 26qa | ||
| 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: | Get mongo-perf at https://github.com/mongodb/mongo , build, and run
and wait for the output of Distinct {With,Without}Index. |
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| Participants: |
| Description |
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mongo-perf shows distinct doesn't scale very well, and the problem gets evident after 4 threads. This is tested on a recent 12-core Xeon. The problem affects every version of mongo I was able to test on (namely 2.2, 2.4, 2.6). Screenshot attached. |
| Comments |
| Comment by Asya Kamsky [ 06/Nov/17 ] |
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I've run some quick tests and confirmed that this seems to only affect MMAPV1. |