Add a make_date function

[Omega359]

Which issue does this PR close?

Closes#9024

Are these changes tested?

Yes, in code and sql logic tests.

Are there any user-facing changes?

A new make_date function is available, documented in user guide with examples in the datafusion-examples module.

[alamb]

Thank you @Omega359 -- this is a really nice contribution. Well documented and well tested.

The implementation also seems to match the postgres documentation https://www.postgresql.org/docs/current/functions-datetime.html

🏆

[alamb]

This could probably be implemented more efficiently with some sort of iterator that wrapped a ColumnarValue and returned i32s -- that way you could iterate over all three arrays with zip and not have to do the downcast eah time, etc

-- and then you could generate specialized implementations for ColumnarValue::Array and ColumnarValue::Scalar

However, given make_date is likely to be run with all constants I don't think there is any pressing need to optimize the implementation unless someone has a particular need for a faster implementation

[Omega359]

Initially I was tempted to try adding an IntoIterator for ColumnarValue that accepted an optional size (for scalar) which returns an option of either the array value at the current pos or the scalar value. That seemed a bit much given my current Rust skill level though.

[alamb]

I think you can write this logic like so to avoid the unwraps below:

Suggested change

	if m.is_err(){
	return exec_err!(
	"Month value '{:?}' is out of range",
	value_fn(&months, i).unwrap()
	);
	}
	letOk(m) = m else{
	return exec_err!(
	"Month value '{:?}' is out of range",
	value_fn(&months, i).unwrap()
	);
	};

[alamb]

Proposed PR to do this in #9072

[alamb]

Thanks again @Omega359

I made a small PR here to remove the unwraps: #9072

Looking more carefully at the code in datetime_expressions.rs think we can probably remove more of the unwraps by using Result::map_err, but I think that is a matter of style (though it would some some runtime checks too)