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https://issues.apache.org/jira/browse/ARROW-14805?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Weston Pace updated ARROW-14805:
--------------------------------
    Labels: ORC c++ dataset good-second-issue  (was: ORC c++ dataset)

> [C++][Dataset] Support Count function without projections in ORC to avoid 
> loading all columns
> ---------------------------------------------------------------------------------------------
>
>                 Key: ARROW-14805
>                 URL: https://issues.apache.org/jira/browse/ARROW-14805
>             Project: Apache Arrow
>          Issue Type: Sub-task
>          Components: C++
>            Reporter: xiangxiang Shen
>            Priority: Major
>              Labels: ORC, c++, dataset, good-second-issue
>
> For ORC support in dataset, when execute count query without projections, 
> just like "select count(*) from table", it will load all columns. Because orc 
> lib code is that 
> [https://github.com/apache/orc/blob/22828f79a526069d9629719c9476b7addad91ae6/c%2B%2B/src/Reader.cc#L120-L144.]
>  
> Arrow side can improve it like parquet in dataset.



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