[ARROW-11402] [C++][Dataset] Allow more aggresive implicit casts for literals

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++
• Labels: dataset pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/18481
• Assignee: Unassigned
• Reporter: Ben Kietzman
• Created: 27/Jan/21 17:20
• Updated: 11/Jan/23 08:19

Description

After ARROW-8919, a literal in an Expression may cause unnecessary implicit casting of a column. For example equal(field_ref("i8"), literal(1)) will cause column i8 to be promoted to the type of the literal (int32) for comparison. Since we have access to the literal value at bind time we could examine 1 and determine that it can safely be *de*moted to int8, which produces a semantically equivalent and more performant filter.

Issue Links

• links to: GitHub Pull Request #15180