From 65776cfa54139de65f482845cde546d5aeaeb6c7 Mon Sep 17 00:00:00 2001
From: alanchuang22-dev <2584829494@qq.com>
Date: Tue, 3 Nov 2026 12:45:23 +0800
Subject: [PATCH 1/2] fix: change condition in
 `hasRemainingGapInPreviousGroup()`

---
 .../operator/process/gapfill/AbstractGapFillOperator.java       | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
index fd9a281b5f49b..473d840ae1c56 100644
--- a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
+++ b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
@@ -224,7 +224,7 @@ public boolean hasNext() throws Exception {
   }
 
   private boolean hasRemainingGapInPreviousGroup() {
-    return lastGroupKey != null && currentTime < endTime;
+    return lastGroupKey != null && currentTime <= endTime;
   }
 
   @Override

From 7330aef57b03655a0d579b464c45a2d5642e015e Mon Sep 17 00:00:00 2001
From: alanchuang22-dev <2584829494@qq.com>
Date: Tue, 3 Nov 2026 16:49:45 +0800
Subject: [PATCH 2/2] fix: add `timeIteratorExhausted` as label

---
 .../gapfill/AbstractGapFillOperator.java      | 22 ++++++++++++-------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
index 473d840ae1c56..4089e4bbca637 100644
--- a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
+++ b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/execution/operator/process/gapfill/AbstractGapFillOperator.java
@@ -59,6 +59,7 @@ abstract class AbstractGapFillOperator implements ProcessOperator {
   private final long endTime;
 
   protected long currentTime;
+  private boolean timeIteratorExhausted;
   private SortKey lastGroupKey = null;
 
   AbstractGapFillOperator(
@@ -140,6 +141,14 @@ public TsBlock next() throws Exception {
 
   private void resetTimeIterator() {
     currentTime = startTime;
+    timeIteratorExhausted = false;
+  }
+
+  private void advanceTimeIterator() {
+    long previousTime = currentTime;
+    nextTime();
+    // Saturation leaves no later timestamp to mark the consumed window across next() calls.
+    timeIteratorExhausted |= currentTime <= previousTime;
   }
 
   private void writeCurrentRow(TsBlock block, int rowIndex) {
@@ -153,7 +162,7 @@ private void writeCurrentRow(TsBlock block, int rowIndex) {
         columnBuilder.write(column, rowIndex);
       }
     }
-    nextTime();
+    advanceTimeIterator();
   }
 
   private void fillGaps(TsBlock block, int rowIndex, long currentEndTime) {
@@ -162,13 +171,10 @@ private void fillGaps(TsBlock block, int rowIndex, long currentEndTime) {
 
   private void fillGaps(
       TsBlock block, int rowIndex, long currentEndTime, boolean endTimeInclusive) {
-    while (currentTime < currentEndTime || (endTimeInclusive && currentTime == currentEndTime)) {
-      long previousTime = currentTime;
+    while (!timeIteratorExhausted
+        && (currentTime < currentEndTime || (endTimeInclusive && currentTime == currentEndTime))) {
       gapFillRow(currentTime, block, rowIndex);
-      nextTime();
-      if (currentTime <= previousTime) {
-        break;
-      }
+      advanceTimeIterator();
     }
   }
 
@@ -224,7 +230,7 @@ public boolean hasNext() throws Exception {
   }
 
   private boolean hasRemainingGapInPreviousGroup() {
-    return lastGroupKey != null && currentTime <= endTime;
+    return lastGroupKey != null && !timeIteratorExhausted && currentTime <= endTime;
   }
 
   @Override