[jira] [Commented] (ARROW-16562) [C++] Avoid slicing array inputs in ExecBatchIterator that would result in one slice

["Wes McKinney (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-16562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17550547#comment-17550547 ] 

Wes McKinney commented on ARROW-16562:
--------------------------------------

As a result of work connected to ARROW-16755, it will no longer be necessary to call {{ArrayData::Slice}} during expression evaluation

> [C++] Avoid slicing array inputs in ExecBatchIterator that would result in one slice
> ------------------------------------------------------------------------------------
>
>                 Key: ARROW-16562
>                 URL: https://issues.apache.org/jira/browse/ARROW-16562
>             Project: Apache Arrow
>          Issue Type: Sub-task
>          Components: C++
>            Reporter: Tobias Zagorni
>            Assignee: Tobias Zagorni
>            Priority: Minor
>              Labels: pull-request-available
>         Attachments: avoid-slicing-performance.txt
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> For scalar functions, {{ExecBatchIterator}} is used to iterate over batches in smaller units. It is implemented by calling {{{}Array::slice(){}}}. For small batches, this is unecessary, since only one slice is created. The slice operation still causes some overhead by copying the shrared_ptrs of the ArrayData object, inclung the type pointer, which can lead to contention (ARROW-16161).
> This Patch checks if the batch size is smaller than the slice size first, and uses std::move in this case.
> I have attached a comparision of the ExecuteScalarExpressionOverhead benchmark here: [^avoid-slicing-performance.txt] 
> (created with --benchmark_min_time=20, the standard low runtime tends to be noisy with this, but also shows a positive tendency)



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