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

["Tobias Zagorni (Jira)" <ji...@apache.org>]

Tobias Zagorni created ARROW-16562:
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             Summary: [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
         Attachments: avoid-slicing-performance.txt

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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