diff --git a/src/mito2/src/read/dedup.rs b/src/mito2/src/read/dedup.rs
index a29781b947..678c03fbf6 100644
--- a/src/mito2/src/read/dedup.rs
+++ b/src/mito2/src/read/dedup.rs
@@ -502,6 +502,9 @@ pub(crate) struct LastNonNullIter<I> {
     /// fetch a new batch.
     /// The batch is always not empty.
     current_batch: Option<Batch>,
+    /// The index of the current row in the current batch.
+    /// more to check issue #5229.
+    current_index: usize,
 }
 
 impl<I> LastNonNullIter<I> {
@@ -513,20 +516,9 @@ impl<I> LastNonNullIter<I> {
             strategy: LastNonNull::new(false),
             metrics: DedupMetrics::default(),
             current_batch: None,
+            current_index: 0,
         }
     }
-
-    /// Finds the index of the first row that has the same timestamp with the next row.
-    /// If no duplicate rows, returns None.
-    fn find_split_index(batch: &Batch) -> Option<usize> {
-        if batch.num_rows() < 2 {
-            return None;
-        }
-
-        // Safety: The batch is not empty.
-        let timestamps = batch.timestamps_native().unwrap();
-        timestamps.windows(2).position(|t| t[0] == t[1])
-    }
 }
 
 impl<I: Iterator<Item = Result<Batch>>> LastNonNullIter<I> {
@@ -541,6 +533,7 @@ impl<I: Iterator<Item = Result<Batch>>> LastNonNullIter<I> {
             };
 
             self.current_batch = iter.next().transpose()?;
+            self.current_index = 0;
             if self.current_batch.is_none() {
                 // The iterator is exhausted.
                 self.iter = None;
@@ -549,17 +542,21 @@ impl<I: Iterator<Item = Result<Batch>>> LastNonNullIter<I> {
         }
 
         if let Some(batch) = &self.current_batch {
-            let Some(index) = Self::find_split_index(batch) else {
-                // No duplicate rows in the current batch.
-                return Ok(self.current_batch.take());
-            };
-
-            let first = batch.slice(0, index + 1);
-            let batch = batch.slice(index + 1, batch.num_rows() - index - 1);
-            // `index` is Some indicates that the batch has at least one row remaining.
-            debug_assert!(!batch.is_empty());
-            self.current_batch = Some(batch);
-            return Ok(Some(first));
+            let n = batch.num_rows();
+            // Safety: The batch is not empty when accessed.
+            let timestamps = batch.timestamps_native().unwrap();
+            let mut pos = self.current_index;
+            while pos + 1 < n && timestamps[pos] != timestamps[pos + 1] {
+                pos += 1;
+            }
+            let segment = batch.slice(self.current_index, pos - self.current_index + 1);
+            if pos + 1 < n && timestamps[pos] == timestamps[pos + 1] {
+                self.current_index = pos + 1;
+            } else {
+                self.current_batch = None;
+                self.current_index = 0;
+            }
+            return Ok(Some(segment));
         }
 
         Ok(None)