Re: [PR] adding more date types [arrow-rs]

["Dandandan (via GitHub)" <gi...@apache.org>]

Dandandan commented on code in PR #5444:
URL: https://github.com/apache/arrow-rs/pull/5444#discussion_r1514241520


##########
arrow-cast/src/parse.rs:
##########
@@ -556,65 +556,30 @@ fn parse_date(string: &str) -> Option<NaiveDate> {
             .map(|dt| dt.date_naive())
             .ok();
     };
-    let mut digits = [0; 10];
-    let mut mask = 0;
-
-    // Treating all bytes the same way, helps LLVM vectorise this correctly
-    for (idx, (o, i)) in digits.iter_mut().zip(string.bytes()).enumerate() {
-        *o = i.wrapping_sub(b'0');
-        mask |= ((*o < 10) as u16) << idx
-    }
-
-    const HYPHEN: u8 = b'-'.wrapping_sub(b'0');
-
-    //  refer to https://www.rfc-editor.org/rfc/rfc3339#section-3
-    if digits[4] != HYPHEN {
-        let (year, month, day) = match (mask, string.len()) {
-            (0b11111111, 8) => (
-                digits[0] as u16 * 1000
-                    + digits[1] as u16 * 100
-                    + digits[2] as u16 * 10
-                    + digits[3] as u16,
-                digits[4] * 10 + digits[5],
-                digits[6] * 10 + digits[7],
-            ),
-            _ => return None,
-        };
-        return NaiveDate::from_ymd_opt(year as _, month as _, day as _);
-    }
-
-    let (month, day) = match mask {
-        0b1101101111 => {
-            if digits[7] != HYPHEN {
-                return None;
-            }
-            (digits[5] * 10 + digits[6], digits[8] * 10 + digits[9])
-        }
-        0b101101111 => {
-            if digits[7] != HYPHEN {
-                return None;
-            }
-            (digits[5] * 10 + digits[6], digits[8])
-        }
-        0b110101111 => {
-            if digits[6] != HYPHEN {
-                return None;
-            }
-            (digits[5], digits[7] * 10 + digits[8])
+    use regex::Regex;

Review Comment:
   You'll want to precompile / reuse the regex. That might  return most of the performance. 



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