[jira] [Commented] (ARROW-11647) [C++][Compute] CastFromNull does not use preallocated buffers

["Ben Kietzman (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-11647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17299123#comment-17299123 ] 

Ben Kietzman commented on ARROW-11647:
--------------------------------------

[~edponce]

> [C++][Compute] CastFromNull does not use preallocated buffers
> -------------------------------------------------------------
>
>                 Key: ARROW-11647
>                 URL: https://issues.apache.org/jira/browse/ARROW-11647
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Ben Kietzman
>            Assignee: Ben Kietzman
>            Priority: Minor
>             Fix For: 4.0.0
>
>
> When casting from null, currently new buffers are allocated for every batch of the computation. This is wasteful as for simple types data buffers are preallocated and the null bitmap is handled separately; CastFromNull need do no work at all (unless we decide to explicitly zero the data buffer). For varlength out types the offsets buffer is preallocated and should be zeroed, for struct types preallocation is not implemented (but should be as simple as preallocating each child array).



--
This message was sent by Atlassian Jira
(v8.3.4#803005)