[jira] [Updated] (ORC-574) Performance: Use const references for string statistics min and max to avoid copy construction

["David Zanter (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ORC-574?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

David Zanter updated ORC-574:
-----------------------------
    Summary: Performance: Use const references for string statistics min and max to avoid copy construction  (was: Performance: Statistics getMax/getMin should return const vals to prevent std:string copies)

> Performance: Use const references for string statistics min and max to avoid copy construction
> ----------------------------------------------------------------------------------------------
>
>                 Key: ORC-574
>                 URL: https://issues.apache.org/jira/browse/ORC-574
>             Project: ORC
>          Issue Type: Improvement
>          Components: C++
>    Affects Versions: 1.6.2
>            Reporter: David Zanter
>            Priority: Major
>         Attachments: callgrind-before-after.JPG
>
>
> Via Callgrind Performance Profiling of a scenario of a Copy (Full Read and then Full Write) of a 1.9 million row ZLib Compressed ORC Table.  The #4 Usage of CPU is the std::string alloc from being called by: orc::StringColumnStatisticsImpl::update method due to the getMax/getMin calls causing std:string alloc/copy/delete.
>  
> Changing the getMaximum/getMinimum methods to return const vals will prevent these alloc/copy/deletes from occurring.
>  
> Currently with 1.6.X master the performance profile of this scenario is:
> Instructions Executed: 16.6 Billion Instructions
> real clock time 3.91 seconds
>  
> With the fix to use consts, this improves the CPU usage by about 38% and the Clock Time about 10% to:
> Instructions Executed: 12.0 Billion Instructions
> real clock time 3.53 seconds
>  
> Attached JPG showing before (left) and after (right) screenshot of callgrind.
>  
>  



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