Different numeric type may be able to compare

[tisonkun]

arrow-rs/arrow-ord/src/cmp.rs

Lines 239 to 243 in 6bf2bda

	} else if l_t != r_t {
	return Err(ArrowError::InvalidArgumentError(format!(
	"Invalid comparison operation: {l_t} {op} {r_t}"
	)));
	}

Crates like num-cmp shows that different numeric type (e.g., u64 and i64) is comparable.

Is it possible to extend arrow array comparison to support compare these two kind of datum?

[tustvold]

The major difficulty here is combinatorial explosion of code generation that would result, something that is already a major issue. This not only bloats binaries but contributes to long compilation times.

Instead what most query engines, such as DataFusion do, is use the cast kernels to coerce the inputs to a common type before performing the comparison. This may not be as optimal as doing the comparison on the heterogenous types, but is likely good enough given such heterogeneous comparisons are comparatively rare.

[alamb]

It is also fairly straightforward to implement your own kernels for specific comparisons if you have special cases that are not handled by arrow-rs (the challenge is mananging the code complexity for all the possible type combinations, as alluded to above by @tustvold )