Yibo Cai created ARROW-8129:
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Summary: [C++][Compute] Refine compare sorting kernel
Key: ARROW-8129
URL: https://issues.apache.org/jira/browse/ARROW-8129
Project: Apache Arrow
Issue Type: Improvement
Reporter: Yibo Cai
Assignee: Yibo Cai
Sorting kernel implements two comparison functions,
[CompareValues|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L67]
use array.Value() for numeric data and
[CompareViews|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L72]
uses array.GetView() for non-numeric ones. It can be simplified by using
GetView() only as all data types support GetView().
To my surprise, benchmark shows about 40% performance improvement after the
change.
After some digging, I find in current code, the [comparison
callback|https://github.com/apache/arrow/blob/ab21f0ee429c2a2c82e4dbc5d216ab1da74221a2/cpp/src/arrow/compute/kernels/sort_to_indices.cc#L94]
is not inlined (check disassembled code), it leads to a function call. It's
very bad for this hot loop. Using only GetView() fixes this issue, code inlined
okay.
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