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From "Aman Sinha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-3759) Make partition pruning multi-phased to reduce the working set kept in memory
Date Fri, 18 Sep 2015 17:15:04 GMT

    [ https://issues.apache.org/jira/browse/DRILL-3759?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14875968#comment-14875968
] 

Aman Sinha commented on DRILL-3759:
-----------------------------------

+1 for the patch.  Good that you added a negative unit test in addition to the positive ones.


> Make partition pruning multi-phased to reduce the working set kept in memory
> ----------------------------------------------------------------------------
>
>                 Key: DRILL-3759
>                 URL: https://issues.apache.org/jira/browse/DRILL-3759
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning & Optimization
>    Affects Versions: 1.1.0
>            Reporter: Aman Sinha
>            Assignee: Aman Sinha
>
> Currently, partition pruning gets all file names in the table and applies the pruning.
 Suppose the files are spread out over several directories and there is a filter  on dirN,
 this is not efficient - both in terms of elapsed time and memory usage.  This has been seen
in a few use cases recently. 
> Wherever possible, we should ideally perform the pruning in N steps (where N is the number
of directory levels referenced in the filter conditions):   
>   1. Get the directory and  filenames at level i
>   2. Materialize into the in-memory table 
>   3. Apply interpreter-based evaluation of filter condition
>   4. Determine qualifying directories, increment i and repeat from step 1
>  
> This multi phase approach may not be possible for certain types of filters - e,g for
disjunctions. This analysis needs to be done. 



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