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

["Deneche A. Hakim (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15227790#comment-15227790 ] 

Deneche A. Hakim edited comment on DRILL-4530 at 4/6/16 6:07 AM:
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I did an experiment where I *hacked* Drill to use protobuf instead of json for the metadata cache. For a customer case with a parquet table with 3 levels of directories and 395250 files, the protobuf cache was 87% smaller than json and loaded 83% faster.


was (Author: adeneche):
I did an experiment where I *hacked* Drill to use protobuf instead of json for the metadata cache and for a customer case with a parquet table with 3 levels of directories and 395250 files, the protobuf cache was 87% smaller than json and loaded 83% faster.

> 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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