diff --git a/source/libs/index/src/index_util.c b/source/libs/index/src/index_util.c
index ecf5e6d36c02a4e1c287756d0b38c4957d4bc810..fcaab968c24a296431f2a25039050947887e0aac 100644
--- a/source/libs/index/src/index_util.c
+++ b/source/libs/index/src/index_util.c
@@ -72,6 +72,11 @@ void iUnion(SArray *inters, SArray *final) {
   if (sz <= 0) {
     return;
   }
+  if (sz == 1) {
+    taosArrayAddAll(final, taosArrayGetP(inters, 0));
+    return;
+  }
+
   MergeIndex *mi = calloc(sz, sizeof(MergeIndex));
   for (int i = 0; i < sz; i++) {
     SArray *t = taosArrayGetP(inters, i);
diff --git a/source/libs/index/test/utilUT.cc b/source/libs/index/test/utilUT.cc
index 89549783444fcc4f2b29a494a57eeae683b79268..ffa4ead7749c52f97042179526d57dad99424d50 100644
--- a/source/libs/index/test/utilUT.cc
+++ b/source/libs/index/test/utilUT.cc
@@ -201,3 +201,27 @@ TEST_F(UtilEnv, 03union) {
   iUnion(src, rslt);
   assert(taosArrayGetSize(rslt) == 9);
 }
+TEST_F(UtilEnv, 04union) {
+  clearSourceArray(src);
+  clearFinalArray(rslt);
+
+  uint64_t arr1[] = {1, 4, 5, 6};
+  SArray * f = (SArray *)taosArrayGetP(src, 0);
+  for (int i = 0; i < sizeof(arr1) / sizeof(arr1[0]); i++) {
+    taosArrayPush(f, &arr1[i]);
+  }
+
+  uint64_t arr2[] = {7, 8, 10};
+  f = (SArray *)taosArrayGetP(src, 1);
+  for (int i = 0; i < sizeof(arr2) / sizeof(arr2[0]); i++) {
+    taosArrayPush(f, &arr2[i]);
+  }
+
+  uint64_t arr3[] = {20, 21, 30, 100};
+  f = (SArray *)taosArrayGetP(src, 2);
+  for (int i = 0; i < sizeof(arr3) / sizeof(arr3[0]); i++) {
+    taosArrayPush(f, &arr3[i]);
+  }
+  iUnion(src, rslt);
+  assert(taosArrayGetSize(rslt) == 11);
+}