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From "Johan Mabille (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (ARROW-602) C++: Provide iterator access to primitive elements inside a Column/ChunkedArray
Date Mon, 20 Mar 2017 01:19:42 GMT

    [ https://issues.apache.org/jira/browse/ARROW-602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15929991#comment-15929991
] 

Johan Mabille edited comment on ARROW-602 at 3/20/17 1:19 AM:
--------------------------------------------------------------

Ok, so it is possible to provide an STL compliant iterator. Cool !
EDIT: still a little problem, the value_type is unknown at compilation, so it might be usefull
to add it as a template parameter of ChunkedArray. Besides, that would allow type checking
in its constructor.

I think most of the use cases would be to apply STL-like algorithms, so it makes sense to
iterate over non-null values only. Later we can provide a "full" iteration interface for the
case where iteration over null values is required, what do you think ?


was (Author: johanmabille):
Ok, so it is possible to provide an STL compliant iterator. Cool !
EDIT: still a little problem, the value_type is unknown at compilation, so it might be usefull
to add it as a template parameter of ChunkedArray. Besides, that you allows type checking
in the its constructor

I think most of the use cases would be to apply STL-like algorithms, so it makes sense to
iterate over non-null values only. Later we can provide a "full" iteration interface for the
case where iteration over null values is required, what do you think ?

> 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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