perf: allow users to skip utf8 validation in arrow-row

arrow-row/src/lib.rs

@@ -1256,6 +1256,14 @@ impl RowConverter {
         RowParser::new(Arc::clone(&self.fields))
     }
 
+    /// Like [`Self::parser`] but skips UTF-8 validation on decode.
+    ///
+    /// # Safety
+    /// The caller must ensure all row bytes contain valid UTF-8 for string columns.
+    pub unsafe fn parser_skip_utf8_validation(&self) -> RowParser {
+        unsafe { RowParser::with_skip_utf8_validate(Arc::clone(&self.fields)) }
+    }
+
     /// Returns the size of this instance in bytes
     ///
     /// Includes the size of `Self`.
@@ -1282,6 +1290,18 @@ impl RowParser {
             },
         }
     }
+    /// Like [`RowConverter::parser`] but skips UTF-8 validation on decode.
+    ///
+    /// # Safety
+    /// The caller must ensure all row bytes contain valid UTF-8 for string columns.
+    unsafe fn with_skip_utf8_validate(fields: Arc<[SortField]>) -> Self {
+        Self {
+            config: RowConfig {
+                fields,
+                validate_utf8: false,
+            },
+        }
+    }
 
     /// Creates a [`Row`] from the provided `bytes`.
     ///
@@ -6676,6 +6696,24 @@ mod tests {
         assert_eq!(rows_iter.next_back(), None);
     }
 
+    /// Round-trip through `with_skip_utf8_validate` confirms skipping validation preserves values.
+    #[test]
+    fn test_row_parser_skip_utf8_validation_roundtrip() {
+        let converter = RowConverter::new(vec![SortField::new(DataType::Utf8)]).unwrap();
+        let array = StringArray::from(vec!["arrow", "rust"]);
+        let rows = converter.convert_columns(&[Arc::new(array) as _]).unwrap();
+        let binary = rows.try_into_binary().expect("fits in i32 offsets");
+
+        // SAFETY: bytes come from this RowConverter and are known-valid UTF-8.
+        let parser = unsafe { RowParser::with_skip_utf8_validate(Arc::clone(&converter.fields)) };
+
+        let decoded = converter
+            .convert_rows(binary.iter().map(|b| parser.parse(b.unwrap())))
+            .unwrap();
+        let got: Vec<_> = decoded[0].as_string::<i32>().iter().flatten().collect();
+        assert_eq!(got, vec!["arrow", "rust"]);
+    }
+
     #[test]
     fn row_iter_next_back() {
         let row_converter = RowConverter::new(vec![SortField::new(DataType::UInt8)]).unwrap();