[jira] [Commented] (DRILL-4530) Improve metadata cache performance for queries with single partition

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15326679#comment-15326679 ] 

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

GitHub user amansinha100 opened a pull request:

    https://github.com/apache/drill/pull/519

    DRILL-4530: Optimize partition pruning with metadata caching for the …

    …single partition case.
    
     - Enhance PruneScanRule to detect single partitions based on referenced dirs in the filter.
     - Keep a new status of EXPANDED_PARTIAL for FileSelection.
     - Create separate .directories metadata file to prune directories first before files.
     - Introduce cacheFileRoot attribute to keep track of the parent directory of the cache file after partition pruning.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/amansinha100/incubator-drill DRILL-4530-1

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/drill/pull/519.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #519
    
----
commit 9c9687e804fa05c8f4b7b065738c458cb88bf5c4
Author: Aman Sinha <as...@maprtech.com>
Date:   2016-03-25T19:55:59Z

    DRILL-4530: Optimize partition pruning with metadata caching for the single partition case.
    
     - Enhance PruneScanRule to detect single partitions based on referenced dirs in the filter.
     - Keep a new status of EXPANDED_PARTIAL for FileSelection.
     - Create separate .directories metadata file to prune directories first before files.
     - Introduce cacheFileRoot attribute to keep track of the parent directory of the cache file after partition pruning.

----


> 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: 1.7.0
>
>
> 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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