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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4530) Improve metadata cache performance for queries with single partition
Date Tue, 12 Jul 2016 21:20:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15373718#comment-15373718
] 

ASF GitHub Bot commented on DRILL-4530:
---------------------------------------

Github user jinfengni commented on a diff in the pull request:

    https://github.com/apache/drill/pull/519#discussion_r70524663
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/FileSystemPartitionDescriptor.java
---
    @@ -212,8 +223,12 @@ public TableScan createTableScan(List<PartitionLocation> newPartitionLocation)
t
         }
     
         if (scanRel instanceof DrillScanRel) {
    -      final FileSelection newFileSelection = new FileSelection(null, newFiles, getBaseTableLocation());
    -      final FileGroupScan newGroupScan = ((FileGroupScan)((DrillScanRel)scanRel).getGroupScan()).clone(newFileSelection);
    +//      final FormatSelection formatSelection = (FormatSelection)((DynamicDrillTable)scanRel.getTable()).getSelection();
    +      final FormatSelection formatSelection = (FormatSelection)table.getSelection();
    +      final FileSelection newFileSelection = new FileSelection(null, newFiles, getBaseTableLocation(),
    +          cacheFileRoot, formatSelection.getSelection().getDirStatus());
    +      final FileGroupScan newGroupScan =
    +          ((FileGroupScan)((DrillScanRel)scanRel).getGroupScan()).clone(newFileSelection,
cacheFileRoot);
    --- End diff --
    
    This newFileSelection already has cacheFileRoot.  Do you think clone() only need take
FileSelection, since FileSelection has cacheFileRoot infor?
    



> Improve metadata cache performance for queries with single partition 
> ---------------------------------------------------------------------
>
>                 Key: DRILL-4530
>                 URL: https://issues.apache.org/jira/browse/DRILL-4530
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning & Optimization
>    Affects Versions: 1.6.0
>            Reporter: Aman Sinha
>            Assignee: Aman Sinha
>             Fix For: Future
>
>
> Consider two types of queries which are run with Parquet metadata caching: 
> {noformat}
> query 1:
> SELECT col FROM  `A/B/C`;
> query 2:
> SELECT col FROM `A` WHERE dir0 = 'B' AND dir1 = 'C';
> {noformat}
> For a certain dataset, the query1 elapsed time is 1 sec whereas query2 elapsed time is
9 sec even though both are accessing the same amount of data.  The user expectation is that
they should perform roughly the same.  The main difference comes from reading the bigger metadata
cache file at the root level 'A' for query2 and then applying the partitioning filter.  query1
reads a much smaller metadata cache file at the subdirectory level. 



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