diff --git a/src/stream/src/executor/over_window/over_partition.rs b/src/stream/src/executor/over_window/over_partition.rs
index f0c230103408f..16116fd37e743 100644
--- a/src/stream/src/executor/over_window/over_partition.rs
+++ b/src/stream/src/executor/over_window/over_partition.rs
@@ -822,14 +822,20 @@ fn find_affected_ranges<'cache>(
         .iter()
         .any(|call| call.frame.bounds.end_is_unbounded());
 
+    // NOTE: Don't be too clever! Here we must calculate `first_frame_start` after calculating
+    // `first_curr_key`, because the correct calculation of `first_frame_start` depends on
+    // `first_curr_key` which is the MINIMUM of all `first_curr_key`s of all frames of all window
+    // function calls.
+
     let first_curr_key = if end_is_unbounded {
         // If the frame end is unbounded, the frame corresponding to the first key is always
         // affected.
         first_key
     } else {
-        calls
-            .iter()
-            .map(|call| match &call.frame.bounds {
+        let mut min_first_curr_key = &Sentinelled::Largest;
+
+        'outer_loop: for call in calls {
+            let key = match &call.frame.bounds {
                 FrameBounds::Rows(bounds) => {
                     let mut cursor = part_with_delta
                         .lower_bound(Bound::Included(delta.first_key_value().unwrap().0));
@@ -838,14 +844,26 @@ fn find_affected_ranges<'cache>(
                         // cursor is at ghost position at first.
                         cursor.move_prev();
                         if cursor.position().is_ghost() {
-                            break;
+                            min_first_curr_key = first_key;
+                            break 'outer_loop;
                         }
                     }
                     cursor.key().unwrap_or(first_key)
                 }
-            })
-            .min()
-            .expect("# of window function calls > 0")
+            };
+            min_first_curr_key = min_first_curr_key.min(key);
+            if min_first_curr_key == first_key {
+                // if we already pushed the affected curr key to the first key, no more pushing is needed
+                break 'outer_loop;
+            }
+        }
+
+        assert!(
+            !min_first_curr_key.is_largest(),
+            "# of window function calls > 0, meaning this must be mutated"
+        );
+
+        min_first_curr_key
     };
 
     let first_frame_start = if start_is_unbounded {
@@ -853,65 +871,104 @@ fn find_affected_ranges<'cache>(
         // range.
         first_key
     } else {
-        calls
-            .iter()
-            .map(|call| match &call.frame.bounds {
+        let mut min_frame_start = &Sentinelled::Largest;
+
+        'outer_loop: for call in calls {
+            let key = match &call.frame.bounds {
                 FrameBounds::Rows(bounds) => {
                     let mut cursor = part_with_delta.find(first_curr_key).unwrap();
                     for _ in 0..bounds.start.n_preceding_rows().unwrap() {
                         cursor.move_prev();
                         if cursor.position().is_ghost() {
-                            break;
+                            min_frame_start = first_key;
+                            break 'outer_loop;
                         }
                     }
                     cursor.key().unwrap_or(first_key)
                 }
-            })
-            .min()
-            .expect("# of window function calls > 0")
+            };
+            min_frame_start = min_frame_start.min(key);
+            if min_frame_start == first_key {
+                // if we already pushed the affected frame start to the first key, no more pushing is needed
+                break 'outer_loop;
+            }
+        }
+
+        assert!(
+            !min_frame_start.is_largest(),
+            "# of window function calls > 0, meaning this must be mutated"
+        );
+
+        min_frame_start
     };
 
     let last_curr_key = if start_is_unbounded {
         last_key
     } else {
-        calls
-            .iter()
-            .map(|call| match &call.frame.bounds {
+        let mut max_last_curr_key = &Sentinelled::Smallest;
+
+        'outer_loop: for call in calls {
+            let key = match &call.frame.bounds {
                 FrameBounds::Rows(bounds) => {
                     let mut cursor = part_with_delta
                         .upper_bound(Bound::Included(delta.last_key_value().unwrap().0));
                     for _ in 0..bounds.start.n_preceding_rows().unwrap() {
                         cursor.move_next();
                         if cursor.position().is_ghost() {
-                            break;
+                            max_last_curr_key = last_key;
+                            break 'outer_loop;
                         }
                     }
                     cursor.key().unwrap_or(last_key)
                 }
-            })
-            .max()
-            .expect("# of window function calls > 0")
+            };
+            max_last_curr_key = max_last_curr_key.max(key);
+            if max_last_curr_key == last_key {
+                // if we already pushed the affected curr key to the last key, no more pushing is needed
+                break 'outer_loop;
+            }
+        }
+
+        assert!(
+            !max_last_curr_key.is_smallest(),
+            "# of window function calls > 0, meaning this must be mutated"
+        );
+
+        max_last_curr_key
     };
 
     let last_frame_end = if end_is_unbounded {
         last_key
     } else {
-        calls
-            .iter()
-            .map(|call| match &call.frame.bounds {
+        let mut max_frame_end = &Sentinelled::Smallest;
+
+        'outer_loop: for call in calls {
+            let key = match &call.frame.bounds {
                 FrameBounds::Rows(bounds) => {
                     let mut cursor = part_with_delta.find(last_curr_key).unwrap();
                     for _ in 0..bounds.end.n_following_rows().unwrap() {
                         cursor.move_next();
                         if cursor.position().is_ghost() {
-                            break;
+                            max_frame_end = last_key;
+                            break 'outer_loop;
                         }
                     }
                     cursor.key().unwrap_or(last_key)
                 }
-            })
-            .max()
-            .expect("# of window function calls > 0")
+            };
+            max_frame_end = max_frame_end.max(key);
+            if max_frame_end == last_key {
+                // if we already pushed the affected frame end to the last key, no more pushing is needed
+                break 'outer_loop;
+            }
+        }
+
+        assert!(
+            !max_frame_end.is_smallest(),
+            "# of window function calls > 0, meaning this must be mutated"
+        );
+
+        max_frame_end
     };
 
     if first_curr_key > last_curr_key {