[jira] [Commented] (ARROW-602) C++: Provide iterator access to primitive elements inside a Column/ChunkedArray

["Antoine Pitrou (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16738172#comment-16738172 ] 

Antoine Pitrou commented on ARROW-602:
--------------------------------------

We have {{ArrayDataVisitor}} now that will tackle many of the use cases of iterator access (though with inversion of control, so you have to define a visitor class which may feel like boilerplate).

The nice thing with the inversion of control is that we may for example optimize {{ArrayDataVisitor}} by unrolling the null bitmap reading loop 8 times.

> C++: Provide iterator access to primitive elements inside a Column/ChunkedArray
> -------------------------------------------------------------------------------
>
>                 Key: ARROW-602
>                 URL: https://issues.apache.org/jira/browse/ARROW-602
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Uwe L. Korn
>            Priority: Major
>              Labels: beginner, newbie
>
> Given a ChunkedArray, an Arrow user must currently iterate over all its chunks and then cast them to their types to extract the primitive memory regions to access the values. A convenient way to access the underlying values would be to offer a function that takes a ChunkedArray and returns a C++ iterator over all elements.
> While this may not be the most performant way to access the underlying data, it should have sufficient performance and adds a convenience layer for new users.



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