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Posted to issues@trafodion.apache.org by "Qifan Chen (JIRA)" <ji...@apache.org> on 2015/10/23 19:34:27 UTC

[jira] [Work started] (TRAFODION-1555) The existing heuristic to not consider MDAM scan is too harsh

     [ https://issues.apache.org/jira/browse/TRAFODION-1555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on TRAFODION-1555 started by Qifan Chen.
---------------------------------------------
> The existing heuristic to not consider MDAM scan is too harsh
> -------------------------------------------------------------
>
>                 Key: TRAFODION-1555
>                 URL: https://issues.apache.org/jira/browse/TRAFODION-1555
>             Project: Apache Trafodion
>          Issue Type: Bug
>          Components: sql-cmp
>            Reporter: Qifan Chen
>            Assignee: Qifan Chen
>             Fix For: 2.0-incubating
>
>
> The heuristic that the majority of the key columns should have key predicates does not consider the UECs associated with each key column.  The heuristic may hurt scan performance when these UECs are very low. 



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