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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-491) Support project push-down into scan operator
Date Thu, 01 May 2014 05:38:15 GMT

    [ https://issues.apache.org/jira/browse/DRILL-491?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13986363#comment-13986363
] 

Jinfeng Ni commented on DRILL-491:
----------------------------------

DRILL-491 is currently basing on DRILL-571, which bases on DRILL-494. 


> Support project push-down into scan operator
> --------------------------------------------
>
>                 Key: DRILL-491
>                 URL: https://issues.apache.org/jira/browse/DRILL-491
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
>         Attachments: DRILL-491.3.patch
>
>
> Currently, the scan operator will read all the columns from the data source, and pass
all the columns to down-stream operator. 
> In order to improve performance of Drill query, we should instead push the project operation
into scan operator.  The scan operator will take as an input a list of columns required to
retrieve. If the query only refers a subset of columns, the scan operator will only have to
retrieve values for the column in the list. 
> It's expected to see performance improvement once project push-down is supported. 



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