Jefffrey commented on code in PR #18363:
URL: https://github.com/apache/datafusion/pull/18363#discussion_r2476748405
##########
datafusion/functions-nested/src/flatten.rs:
##########
@@ -154,7 +158,32 @@ pub fn flatten_inner(args: &[ArrayRef]) ->
Result<ArrayRef> {
Ok(Arc::new(flattened_array) as ArrayRef)
}
LargeList(_) => {
- exec_err!("flatten does not support type '{:?}'",
array.data_type())?
+ let (inner_field, inner_offsets, inner_values, _) =
+ as_large_list_array(&values)?.clone().into_parts();
+ // Try to downcast the inner offsets to i32
+ match downcast_i64_inner_to_i32(&inner_offsets, &offsets) {
+ Ok(i32offsets) => {
+ let flattened_array = GenericListArray::<i32>::new(
+ inner_field,
+ i32offsets,
+ inner_values,
+ nulls,
+ );
+ Ok(Arc::new(flattened_array) as ArrayRef)
+ }
+ // If downcast fails we keep the offsets as is
+ Err(_) => {
+ // Fallback: keep i64 offsets → LargeList<i64>
+ let i64offsets = keep_offsets_i64(inner_offsets,
offsets);
+ let flattened_array = GenericListArray::<i64>::new(
+ inner_field,
+ i64offsets,
+ inner_values,
+ nulls,
+ );
+ Ok(Arc::new(flattened_array) as ArrayRef)
Review Comment:
Yep I did mention that, however I did make a note that:
> though this might be tricky considering `return_type()` wouldn't know this
until execution
I think we make a choice, either always upcast to large if one of the inner
lists is a large list, or just error.
I guess the former is more favourable/robust than the latter.
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