Function arrow::compute::kernels::substring::substring

pub fn substring(
    array: &dyn Array, 
    start: i64, 
    length: &Option<u64>
) -> Result<ArrayRef>

Returns an ArrayRef with substrings of all the elements in array.

Arguments

• start - The start index of all substrings. If start >= 0, then count from the start of the string, otherwise count from the end of the string.

• length(option) - The length of all substrings. If length is None, then the substring is from start to the end of the string.

Attention: Both start and length are counted by byte, not by char.

Warning

This function might return in invalid utf-8 format if the character length falls on a non-utf8 boundary, which we hope to fix in a future release.

Example of getting an invalid substring

let array = StringArray::from(vec![Some("E=mc²")]);
let result = substring(&array, -1, &None).unwrap();
let result = result.as_any().downcast_ref::<StringArray>().unwrap();
assert_eq!(result.value(0).as_bytes(), &[0x00B2]); // invalid utf-8 format

Error

this function errors when the passed array is not a [Large]String array.