diff --git a/source/libs/index/src/indexFstDfa.c b/source/libs/index/src/indexFstDfa.c
index b8ac3bd3f54ec8578b87e14cacb713c0247d021b..046ed0f4f4a16bc63fb588c850784d6a1ae066e7 100644
--- a/source/libs/index/src/indexFstDfa.c
+++ b/source/libs/index/src/indexFstDfa.c
@@ -126,7 +126,6 @@ bool dfaBuilderCacheState(FstDfaBuilder *builder, FstSparseSet *set, uint32_t *r
 
   for (int i = 0; i < sparSetLen(set); i++) {
     int32_t ip;
-
     if (false == sparSetGet(set, i, &ip)) continue;
 
     Inst *inst = taosArrayGet(builder->dfa->insts, ip);
diff --git a/source/libs/index/src/indexFstRegex.c b/source/libs/index/src/indexFstRegex.c
index 0189e9fe6e13ffa3532937303ff3b5fb9366bd1b..e148f211f23a6acbf9bd81eed2dff13761a7800a 100644
--- a/source/libs/index/src/indexFstRegex.c
+++ b/source/libs/index/src/indexFstRegex.c
@@ -22,11 +22,8 @@ FstRegex *regexCreate(const char *str) {
   if (regex == NULL) {
     return NULL;
   }
-  int32_t sz = (int32_t)strlen(str);
-  char   *orig = taosMemoryCalloc(1, sz);
-  memcpy(orig, str, sz);
 
-  regex->orig = orig;
+  regex->orig = tstrdup(str);
 
   // construct insts based on str
   SArray *insts = taosArrayInit(256, sizeof(uint8_t));
diff --git a/source/libs/index/src/indexFstSparse.c b/source/libs/index/src/indexFstSparse.c
index 5fdd797aa8584f8fcb77e830219e5cba7e4802f3..60eb7afd90277def52d473a49461256c88608c04 100644
--- a/source/libs/index/src/indexFstSparse.c
+++ b/source/libs/index/src/indexFstSparse.c
@@ -52,7 +52,7 @@ bool sparSetAdd(FstSparseSet *ss, int32_t ip, int32_t *idx) {
   if (ss == NULL) {
     return false;
   }
-  if (ip >= ss->cap) {
+  if (ip >= ss->cap || ip < 0) {
     return false;
   }
   uint32_t i = ss->size;
@@ -65,7 +65,7 @@ bool sparSetAdd(FstSparseSet *ss, int32_t ip, int32_t *idx) {
   return true;
 }
 bool sparSetGet(FstSparseSet *ss, int32_t idx, int32_t *ip) {
-  if (idx >= ss->cap || idx >= ss->size) {
+  if (idx >= ss->cap || idx >= ss->size || idx < 0) {
     return false;
   }
   int32_t val = ss->dense[idx];
@@ -75,12 +75,12 @@ bool sparSetGet(FstSparseSet *ss, int32_t idx, int32_t *ip) {
   return val == -1 ? false : true;
 }
 bool sparSetContains(FstSparseSet *ss, int32_t ip) {
-  if (ip >= ss->cap) {
+  if (ip >= ss->cap || ip < 0) {
     return false;
   }
   int32_t i = ss->sparse[ip];
 
-  if (i < ss->cap && i < ss->size && ss->dense[i] == ip) {
+  if (i >= 0 && i < ss->cap && i < ss->size && ss->dense[i] == ip) {
     return true;
   } else {
     return false;