[SERVER-12651] Unindexed distinct queries regression (wrt 2.4) Created: 07/Feb/14 Updated: 11/Jul/16 Resolved: 12/Feb/14 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Querying |
| Affects Version/s: | 2.5.5 |
| Fix Version/s: | 2.6.0-rc0 |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Davide Italiano | Assignee: | Benety Goh |
| Resolution: | Done | Votes: | 0 |
| Labels: | 26qa, Performance | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Attachments: |
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| Backwards Compatibility: | Fully Compatible |
| Operating System: | ALL |
| Participants: |
| Description |
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Unindexed distinct queries are slower in 2.6 WRT 2.4, and this is noticeable both in single-threaded and multi-threaded tests I ran. An easy (single-threaded) way to reproduce it can be found attached. 27fb434eaebc35646cdadf7acac562aa47c06ac8 (HEAD as per today) output:
2.4.9 output:
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| Comments |
| Comment by Githook User [ 12/Feb/14 ] | |||||||||||
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Author: {u'username': u'benety', u'name': u'Benety Goh', u'email': u'benety@mongodb.com'}Message: | |||||||||||
| Comment by Davide Italiano [ 07/Feb/14 ] | |||||||||||
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Apparently the biggest offender is ProjectionExec::transform.
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| Comment by Davide Italiano [ 07/Feb/14 ] | |||||||||||
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Attach profiling output + pprof (top 5) output:
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