Implement physical optimizer rule to apply type coercion to physical plans

[andygrove]

Is your feature request related to a problem or challenge?

For DataFusion users who are starting with physical plans rather than logical plans, a physical optimizer rule to apply type coercion to physical plans would be helpful.

See the discussion in #14283 (comment) for one example where this would be helpful.

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

No response

[alamb]

BTW this might be fairly straightforward to add as an extension in comet (maybe it doesn't have to be in the datafusion core if it is only used by systems that use the physical plan)

[edmondop]

Is it possible to do type coercion only at the physical layer? Or does it bring benefits at the logical layer so that we need to do type coercion twice, once at the logical layer for users of the "datafusion frontend" and once at the physical layer for applications like Comet that "skips" the datafusion frontend?

[andygrove]

BTW this might be fairly straightforward to add as an extension in comet (maybe it doesn't have to be in the datafusion core if it is only used by systems that use the physical plan)

We will probably do this in the short term, but don't we want DataFusion to be supported for the execution engine use case, similar to Velox?