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https://issues.apache.org/jira/browse/DRILL-3901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14945545#comment-14945545
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Aman Sinha commented on DRILL-3901:
-----------------------------------

I should add that the normal performance tests over TPCH sf100 don't show a 
regression probably because the number of files is relatively small.  The 
performance test with 100K and more files is a manual test that we started 
tracking recently since Drill users are having hundreds of thousands of files. 

> Performance regression with doing Explain of COUNT(*) over 100K files
> ---------------------------------------------------------------------
>
>                 Key: DRILL-3901
>                 URL: https://issues.apache.org/jira/browse/DRILL-3901
>             Project: Apache Drill
>          Issue Type: Bug
>    Affects Versions: 1.1.0
>            Reporter: Aman Sinha
>            Assignee: Mehant Baid
>
> We are seeing a performance regression when doing an Explain of SELECT 
> COUNT(*) over 100K files in a flat directory (no subdirectories) on latest 
> master branch compared to a run that was done on Sept 26.   Some initial 
> details (I will have more later): 
> {code}
> master branch on Sept 26
>    No metadata cache: 71.452 secs
>    With metadata cache: 15.804 secs
> Latest master branch 
>    No metadata cache: 110 secs
>    With metadata cache: 32 secs
> {code}
> So, both cases show regression.  
> [~mehant] and I took an initial look at this and it appears we might be doing 
> the directory expansion twice.  
>    



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