Fix comment

velox/exec/Window.cpp

@@ -294,6 +294,15 @@ void updateKRowsOffsetsColumn(
   }
 }
 
+// Get the start index that integer overflow can happen for kFollowing.
+FOLLY_ALWAYS_INLINE int32_t getOverflowStart(int64_t constantOffset) {
+  if (constantOffset > (int64_t)std::numeric_limits<int32_t>::max()) {
+    return 0;
+  } else {
+    return std::numeric_limits<int32_t>::max() - constantOffset + 1;
+  }
+}
+
 } // namespace
 
 void Window::updateKRowsFrameBounds(
@@ -306,14 +315,28 @@ void Window::updateKRowsFrameBounds(
     auto constantOffset = frameArg.constant.value();
     auto startValue =
         (isKPreceding ? -constantOffset : constantOffset) + startRow;
-    for (int i = 0; i < numRows; i++) {
-      // Considers integer overflow case.
-      if (startValue != (int32_t)startValue) {
-        rawFrameBounds[i] = startValue < 0 ? 0 : numRows - 1;
+
+    if (isKPreceding) {
+      // Considers a very large int64 constantOffset is used.
+      if (startValue < std::numeric_limits<int32_t>::min()) {
+        std::fill_n(rawFrameBounds, numRows, startRow);
+      } else {
+        // Integer overflow cannot happen.
+        std::iota(rawFrameBounds, rawFrameBounds + numRows, startValue);
+      }
+    } else {
+      auto overflowStart = getOverflowStart(constantOffset);
+      if (overflowStart >= 0 && overflowStart < numRows) {
+        std::iota(rawFrameBounds, rawFrameBounds + overflowStart, startValue);
+        // For remaining, set with the largest index for this partition.
+        std::fill_n(
+            rawFrameBounds + overflowStart,
+            numRows - overflowStart,
+            startRow + numRows - 1);
       } else {
-        rawFrameBounds[i] = startValue;
+        // Integer overflow cannot happen.
+        std::iota(rawFrameBounds, rawFrameBounds + numRows, startValue);
       }
-      startValue = startValue + 1;
     }
   } else {
     currentPartition_->extractColumn(