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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] [Commented] (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:comment-tabpanel&focusedCommentId=14971423#comment-14971423 ] 

Qifan Chen commented on TRAFODION-1555:
---------------------------------------

The heuristic is disabled for now and can be turned on via CQD MDAM_APPLY_RESTRICTION_CHECK.

> 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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