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Partitioned Columnstore Index Defaults to Estimated Rowcount 1 with Primary Key by wBob



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Type: Bug
ID: 808388
Opened: 11/12/2013 1:51:35 PM
Access Restriction: Public
User(s) can reproduce this bug


Estimated Rowcount for columnstore index scan defaults to 1 with moderately complex data warehouse query against partitioned table with primary key. Actual rowcount can be millions. Bad CE can result in Nested Loops and poor performance.
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Posted by swasheck on 7/2/2014 at 12:29 PM
Is there an update available that addresses this issue?
Posted by Microsoft on 1/5/2014 at 7:22 PM
Thanks for submitting this feedback. This issue has been resolved. A fix will be available in an upcoming release of SQL Server. We will update you when the fix has been shipped. Thanks for your continued support in impoving SQL Server.
Posted by NigelRivett on 11/13/2013 at 2:08 AM
I was the first to report this bug and it is causing me a lot of grief.
For the moment we are using the forcescan index hint to get around it but the user access is via a view and this means exposing the underlying object.
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Posted by wBob on 11/12/2013 at 1:53 PM
There are a number of workarounds ( see attached script for demos of some ):

This query can run in less than 1 second with any of:
- FORCESCAN on columnstore
- primary key dropped
- no partition scheme at all
- non-partitioned columnstore
File Name Submitted By Submitted On File Size  
Partitioned Columnstore Index CE Issue.sql 11/12/2013 17 KB