Dandandan commented on a change in pull request #9654:
URL: https://github.com/apache/arrow/pull/9654#discussion_r589762510
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File path: rust/datafusion/src/physical_plan/string_expressions.rs
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@@ -794,85 +525,57 @@ pub fn rtrim<T: StringOffsetSizeTrait>(args: &[ArrayRef])
-> Result<ArrayRef> {
}
}
-/// Extracts the substring of string starting at the start'th character, and
extending for count characters if that is specified. (Same as substring(string
from start for count).)
-/// substr('alphabet', 3) = 'phabet'
-/// substr('alphabet', 3, 2) = 'ph'
-pub fn substr<T: StringOffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef>
{
- match args.len() {
- 2 => {
- let string_array = downcast_string_arg!(args[0], "string", T);
- let start_array = downcast_arg!(args[1], "start", Int64Array);
+/// Splits string at occurrences of delimiter and returns the n'th field
(counting from one).
+/// split_part('abc~@~def~@~ghi', '~@~', 2) = 'def'
+pub fn split_part<T: StringOffsetSizeTrait>(args: &[ArrayRef]) ->
Result<ArrayRef> {
+ let string_array = downcast_string_arg!(args[0], "string", T);
+ let delimiter_array = downcast_string_arg!(args[1], "delimiter", T);
+ let n_array = downcast_arg!(args[2], "n", Int64Array);
- let result = string_array
- .iter()
- .zip(start_array.iter())
- .map(|(string, start)| match (string, start) {
- (None, _) => None,
- (_, None) => None,
- (Some(string), Some(start)) => {
- if start <= 0 {
- Some(string.to_string())
- } else {
- let graphemes =
string.graphemes(true).collect::<Vec<&str>>();
- let start_pos = start as usize - 1;
- if graphemes.len() < start_pos {
- Some("".to_string())
- } else {
- Some(graphemes[start_pos..].concat())
- }
- }
+ let result = string_array
+ .iter()
+ .zip(delimiter_array.iter())
+ .zip(n_array.iter())
+ .map(|((string, delimiter), n)| match (string, delimiter, n) {
+ (None, _, _) => Ok(None),
Review comment:
Here the same, could be `_ -> Ok(None)`
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