[GitHub] [arrow-rs] tustvold commented on a diff in pull request #4399: Faster UTF-8 truncation

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

tustvold commented on code in PR #4399:
URL: https://github.com/apache/arrow-rs/pull/4399#discussion_r1226382289


##########
parquet/src/column/writer/mod.rs:
##########
@@ -1188,30 +1188,11 @@ fn compare_greater_byte_array_decimals(a: &[u8], b: &[u8]) -> bool {
     (a[1..]) > (b[1..])
 }
 
-/// Truncate a UTF8 slice to the longest prefix that is still a valid UTF8 string, while being less than `length` bytes.
+/// Truncate a UTF8 slice to the longest prefix that is still a valid UTF8 string,
+/// while being less than `length` bytes and non-empty
 fn truncate_utf8(data: &str, length: usize) -> Option<Vec<u8>> {
-    // We return values like that at an earlier stage in the process.
-    assert!(data.len() >= length);
-    let mut char_indices = data.char_indices();
-
-    // We know `data` is a valid UTF8 encoded string, which means it has at least one valid UTF8 byte, which will make this loop exist.
-    while let Some((idx, c)) = char_indices.next_back() {
-        let split_point = idx + c.len_utf8();
-        if split_point <= length {
-            return data.as_bytes()[0..split_point].to_vec().into();
-        }
-    }
-
-    None
-}
-
-/// Truncate a binary slice to make sure its length is less than `length`
-fn truncate_binary(data: &[u8], length: usize) -> Option<Vec<u8>> {

Review Comment:
   This method seemed a touch redundant so I opted to remove it



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