neilconway commented on code in PR #20459:
URL: https://github.com/apache/datafusion/pull/20459#discussion_r2841191967
##########
datafusion/common/src/scalar/mod.rs:
##########
@@ -3434,13 +3434,22 @@ impl ScalarValue {
}
}
+ /// Repeats the rows of `arr` `size` times, producing an array with
+ /// `arr.len() * size` total rows.
fn list_to_array_of_size(arr: &dyn Array, size: usize) -> Result<ArrayRef>
{
- let arrays = repeat_n(arr, size).collect::<Vec<_>>();
- let ret = match !arrays.is_empty() {
- true => arrow::compute::concat(arrays.as_slice())?,
- false => arr.slice(0, 0),
- };
- Ok(ret)
+ if size == 0 {
+ return Ok(arr.slice(0, 0));
+ }
+
+ // Examples: given `arr = [[A, B, C]]` and `size = 3`, `indices = [0,
0, 0]` and
+ // the result is `[[A, B, C], [A, B, C], [A, B, C]]`.
+ //
+ // Given `arr = [[A, B], [C]]` and `size = 2`, `indices = [0, 1, 0,
1]` and the
+ // result is `[[A, B], [C], [A, B], [C]]`. (But in practice, we are
always called
Review Comment:
Personally, I'm inclined to leave it as-is: with the comment giving some
examples, the behavior seems reasonably clear to me, and it's not more code to
handle the `arr.len() > 1` case. But lmk if you disagree.
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