[SERVER-24401] Allow fast-distinct scan on indexes with non-simple collation Created: 03/Jun/16  Updated: 03/May/17  Resolved: 18/Aug/16

Status: Closed
Project: Core Server
Component/s: Querying
Affects Version/s: None
Fix Version/s: 3.3.12

Type: Improvement Priority: Major - P3
Reporter: Tess Avitabile (Inactive) Assignee: David Storch
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
related to SERVER-28952 Multikey indexes should not be eligib... Closed
Backwards Compatibility: Fully Compatible
Sprint: Query 2016-08-29
Participants:

 Description   

In getExecutorDistinct(), we use the function turnIxscanIntoDistinctIxscan() to convert an IXSCAN into a DISTINCT_SCAN in a QuerySolution where possible. It only applies to solutions with a PROJECTION as the root, and an IXSCAN as its child. This will not apply to indexes with non-simple collation, because there the IXSCAN stage is always followed by a FETCH stage. It should be possible to convert the IXSCAN into a DISTINCT_SCAN for an index with a non-simple collation anywhere that it is possible for an index with a simple collation.



 Comments   
Comment by Githook User [ 18/Aug/16 ]

Author:

{u'username': u'dstorch', u'name': u'David Storch', u'email': u'david.storch@10gen.com'}

Message: SERVER-24401 allow DISTINCT_SCAN plans over collator comparison keys
Branch: master
https://github.com/mongodb/mongo/commit/bc8096859cdd734012d76e4e192f427ac94e48d7

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