simonvandel commented on code in PR #14675:
URL: https://github.com/apache/datafusion/pull/14675#discussion_r1957081225
##########
datafusion/functions/src/string/uuid.rs:
##########
@@ -87,7 +88,13 @@ impl ScalarUDFImpl for UuidFunc {
if !args.is_empty() {
return internal_err!("{} function does not accept arguments",
self.name());
}
- let values = std::iter::repeat_with(||
Uuid::new_v4().to_string()).take(num_rows);
+
+ // Generate random u128 values
+ let mut rng = rand::thread_rng();
+ let mut randoms = vec![0u128; num_rows];
+ rng.fill(&mut randoms[..]);
+
+ let values = randoms.into_iter().map(|x|
Uuid::from_u128(x).to_string());
Review Comment:
I tried calling `Uuid::new_v4()` instead of `Uuid::from_u128` with
thread_rng. The performance was the same as before this PR.
I think the performance comes from not having to repeatedly call the rng for
bytes. Instead, num_rows*36 bytes can be rng'ed at once.
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