[ARROW-16280] [C++] Avoid copying shared_ptr in Expression::type()

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 8.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/31672
• Assignee: Tobias Zagorni
• Reporter: Tobias Zagorni
• Created: 22/Apr/22 12:02
• Updated: 11/Jan/23 11:43
• Resolved: 22/Apr/22 20:05

Description

Split off from ARROW-16161, since this is a fairly straightforward fix and completely independent of ExecBatch.

Expression::type() currently copies a shared_ptr<DataType>, while the return value is often used directly. We can avoid copying the shared_ptr, by returning a reference to it. This reduces thread contention on these shared_ptrs (ARROW-16161).

Issue Links

• links to: GitHub Pull Request #12957