[ARROW-4628] [Rust] [DataFusion] Implement type coercion query optimizer rule

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.12.0
• Fix Version/s: 0.13.0
• Component/s: Rust, Rust - DataFusion
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/15985
• Assignee: Andy Grove
• Reporter: Andy Grove
• Created: 19/Feb/19 15:09
• Updated: 11/Jan/23 07:35
• Resolved: 21/Mar/19 19:11

Description

Now that we have a query optimizer, we should re-implement type coercion as an optimizer rule that rewrites expressions with explicit casts where required, so that at runtime we are only comparing like types.

For example, the expression float_column < int_column would be rewritten as float_column < CAST(int_column AS float).

DataFusion already has this logic but the current implementation is somewhat hacky and incomplete. Moving it to the optimizer will allow us to implement this correctly.

Issue Links

• links to: GitHub Pull Request #3939