[ARROW-7151] [C++][Dataset] Refactor ExpressionEvaluator to yield Arrays

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Component/s: C++
• External issue URL: https://github.com/apache/arrow/issues/23453
• Assignee: Ben Kietzman
• Reporter: Ben Kietzman
• Created: 12/Nov/19 20:40
• Updated: 11/Jan/23 07:51
• Resolved: 14/Mar/20 00:24

Description

Currently expressions can be evaluated to scalars or arrays, mostly to accomodate ScalarExpression. Instead let all expressions be evaluable to Array only. ScalarExpression will evaluate to an array of repeated values, but expressions whose corresponding kernels can accept a scalar directly (comparison, for example) can avoid materializing this array.