comphead commented on code in PR #2760: URL: https://github.com/apache/datafusion-comet/pull/2760#discussion_r2515239766
########## docs/source/user-guide/latest/compatibility.md: ########## @@ -191,3 +191,57 @@ The following cast operations are not compatible with Spark for all inputs and a Any cast not listed in the previous tables is currently unsupported. We are working on adding more. See the [tracking issue](https://github.com/apache/datafusion-comet/issues/286) for more details. + +### Complex Type Casting + +Comet provides support for casting involving complex types (arrays, structs, and maps) with the following rules: + +#### Array Type Casting + +- **Array to String**: Arrays can be cast to string. The cast is compatible if the element type can be cast to string. + - Recursively checks that the array element type supports casting to string + - Example: `CAST(array(1, 2, 3) AS STRING)` → `"[1, 2, 3]"` + +- **Array to Array**: Arrays can be cast to other array types if the element types are compatible. + - Recursively validates that the source element type can be cast to the target element type + - Example: `CAST(array(1, 2, 3) AS ARRAY<BIGINT>)` → `array(1L, 2L, 3L)` + - The compatibility level (Compatible/Incompatible/Unsupported) is determined by the element type cast + +- **Special case**: Arrays with `NullType` elements (empty arrays) can be cast to any array type + +#### Struct Type Casting + +- **Struct to Struct**: Structs can be cast to other struct types if all field types are compatible. + - Requires the same number of fields in source and target structs Review Comment: Thanks @martin-g appreciate if you can provide an example. so it would be more clear for the user and we can also track this in the issue as future work -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
