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From "Uwe L. Korn (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ARROW-602) C++: Provide iterator access to primitive elements inside a Column/ChunkedArray
Date Fri, 17 Mar 2017 13:34:41 GMT

    [ https://issues.apache.org/jira/browse/ARROW-602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15929977#comment-15929977
] 

Uwe L. Korn commented on ARROW-602:
-----------------------------------

A chunked array is just a collection of arrays of the same type, so we should be able to construct
instances of {{std::iterator<int64_t, ...>}}. The iterator would then iterate over all
the values in all these underlying arrays.

As Arrow arrays are nullable, the iterator must either be on {{std::pair<bool, value_type>}}
or we would have to specify that the iterator only iterates over all non-null values.

> 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
>              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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