[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3801: Faster timestamp parsing (~70-90% faster)

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

tustvold commented on code in PR #3801:
URL: https://github.com/apache/arrow-rs/pull/3801#discussion_r1129934411


##########
arrow-cast/src/parse.rs:
##########
@@ -15,11 +15,117 @@
 // specific language governing permissions and limitations
 // under the License.
 
+use arrow_array::timezone::Tz;
 use arrow_array::types::*;
 use arrow_array::ArrowPrimitiveType;
 use arrow_schema::ArrowError;
 use chrono::prelude::*;
 
+/// Helper for parsing timestamps
+struct TimestampParser {
+    digits: [u8; 32],
+    mask: u32,
+}
+
+impl TimestampParser {
+    fn new(bytes: &[u8]) -> Self {
+        let mut digits = [0; 32];
+        let mut mask = 0;
+
+        for (idx, (o, i)) in digits.iter_mut().zip(bytes).enumerate() {

Review Comment:
   Yeah, LLVM does vectorise it automatically, not especially well, but it does sort of



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