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Date: Fri, 17 Mar 2017 13:34:41 +0000 (UTC)
From: "Uwe L. Korn (JIRA)" <jira@apache.org>
To: dev@arrow.apache.org
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Subject: [jira] [Commented] (ARROW-602) C++: Provide iterator access to
 primitive elements inside a Column/ChunkedArray
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archived-at: Fri, 17 Mar 2017 13:34:52 -0000


    [ 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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