chore

Author: Weijun-H

arrow-cast/src/cast/run_array.rs

@@ -15,10 +15,8 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::vec;
-
 use crate::cast::*;
-use arrow_array::Array;
+use arrow_array::{Array, ArrayRef};
 
 /// Attempts to cast a `RunArray` with index type K into
 /// `to_type` for supported types.
@@ -137,18 +135,7 @@ pub(crate) fn cast_to_run_end_encoded<K: RunEndIndexType>(
     }
 
     // Identify run boundaries by comparing consecutive values
-    let mut run_ends = Vec::new();
-    let mut values_indexes = vec![0usize]; // Always include the first index
-    let mut current_data = cast_array.slice(0, 1).to_data();
-    for idx in 1..cast_array.len() {
-        let next_data = cast_array.slice(idx, 1).to_data();
-        if current_data != next_data {
-            run_ends.push(idx);
-            values_indexes.push(idx);
-            current_data = next_data;
-        }
-    }
-    run_ends.push(cast_array.len());
+    let (run_ends, values_indexes) = compute_run_boundaries(cast_array);
 
     // Build the run_ends array
     for run_end in run_ends {
@@ -167,3 +154,23 @@ pub(crate) fn cast_to_run_end_encoded<K: RunEndIndexType>(
     let run_array = RunArray::<K>::try_new(&run_ends_array, values_array.as_ref())?;
     Ok(Arc::new(run_array))
 }
+
+fn compute_run_boundaries(array: &ArrayRef) -> (Vec<usize>, Vec<usize>) {
+    let mut run_ends = Vec::new();
+    let mut values_indexes = Vec::new();
+    if array.is_empty() {
+        return (run_ends, values_indexes);
+    }
+    values_indexes.push(0);
+    let mut current_data = array.slice(0, 1).to_data();
+    for idx in 1..array.len() {
+        let next_data = array.slice(idx, 1).to_data();
+        if current_data != next_data {
+            run_ends.push(idx);
+            values_indexes.push(idx);
+            current_data = next_data;
+        }
+    }
+    run_ends.push(array.len());
+    (run_ends, values_indexes)
+}