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Date: Thu, 7 Jul 2016 22:58:11 +0000 (UTC)
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Subject: [jira] [Commented] (DRILL-4530) Improve metadata cache performance
 for queries with single partition
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archived-at: Thu, 07 Jul 2016 22:58:13 -0000


    [ https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15366919#comment-15366919 ] 

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

Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/519#discussion_r70002368
  
    --- Diff: contrib/storage-hive/core/src/main/java/org/apache/drill/exec/planner/sql/HivePartitionDescriptor.java ---
    @@ -151,7 +152,7 @@ protected void createPartitionSublists() {
       }
     
       @Override
    -  public TableScan createTableScan(List<PartitionLocation> newPartitions) throws Exception {
    +  public TableScan createTableScan(List<PartitionLocation> newPartitions, String cacheFileRoot) throws Exception {
    --- End diff --
    
    Refactored this interface method.  Updated the PR with a separate commit.


> 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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