XiangpengHao commented on code in PR #6180:
URL: https://github.com/apache/arrow-rs/pull/6180#discussion_r1702421773
##########
arrow-cast/src/cast/mod.rs:
##########
@@ -2417,6 +2436,37 @@ where
Ok(Arc::new(byte_array_builder.finish()))
}
+/// Specialized function to cast from one `ByteViewType` array to
`ByteArrayType` array.
+/// Equvilent to [`cast_view_to_byte`] but with additional constraint on the
`FROM::Native` type.
+fn cast_slice_view_to_byte<FROM, TO>(array: &dyn Array) -> Result<ArrayRef,
ArrowError>
+where
+ FROM: ByteViewType,
+ TO: ByteArrayType,
+ FROM::Native: AsRef<[u8]>,
+ str: AsRef<TO::Native>,
+{
+ let data = array.to_data();
+ let view_array = GenericByteViewArray::<FROM>::from(data);
+
+ let len = view_array.len();
+ let bytes = view_array
+ .views()
+ .iter()
+ .map(|v| ByteView::from(*v).length as usize)
+ .sum::<usize>();
+
+ let mut byte_array_builder = GenericByteBuilder::<TO>::with_capacity(len,
bytes);
+
+ for val in view_array.iter() {
Review Comment:
One way to do this is to create a BinaryArray first, then cast it to
StringArray if necessary:
https://github.com/apache/arrow-rs/blob/master/arrow-array/src/array/string_array.rs#L76-L82
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