diff --git a/source/libs/index/inc/indexFstSparse.h b/source/libs/index/inc/indexFstSparse.h
index 665fb2ba5cb9c0c426e9f3bf345351deed1d4abb..bd704fb427002424e6d4635fa3fef1366bdf9fb9 100644
--- a/source/libs/index/inc/indexFstSparse.h
+++ b/source/libs/index/inc/indexFstSparse.h
@@ -23,17 +23,18 @@ extern "C" {
 #endif
 
 typedef struct FstSparseSet {
-  uint32_t *dense;
-  uint32_t *sparse;
-  int32_t   size;
+  int32_t *dense;
+  int32_t *sparse;
+  int32_t  size;
+  int32_t  cap;
 } FstSparseSet;
 
 FstSparseSet *sparSetCreate(int32_t sz);
 void          sparSetDestroy(FstSparseSet *s);
 uint32_t      sparSetLen(FstSparseSet *ss);
-uint32_t      sparSetAdd(FstSparseSet *ss, uint32_t ip);
-uint32_t      sparSetGet(FstSparseSet *ss, uint32_t i);
-bool          sparSetContains(FstSparseSet *ss, uint32_t ip);
+bool          sparSetAdd(FstSparseSet *ss, int32_t ip, int32_t *val);
+bool          sparSetGet(FstSparseSet *ss, int32_t i, int32_t *val);
+bool          sparSetContains(FstSparseSet *ss, int32_t ip);
 void          sparSetClear(FstSparseSet *ss);
 
 #ifdef __cplusplus
diff --git a/source/libs/index/src/indexFstDfa.c b/source/libs/index/src/indexFstDfa.c
index b820f16a2a00f3ca13453bcc61034e840b79ccb2..275580ebdc239c97bff13c90778134e64f8ad25b 100644
--- a/source/libs/index/src/indexFstDfa.c
+++ b/source/libs/index/src/indexFstDfa.c
@@ -105,8 +105,9 @@ bool dfaBuilderRunState(FstDfaBuilder *builder, FstSparseSet *cur, FstSparseSet
   sparSetClear(cur);
   DfaState *t = taosArrayGet(builder->dfa->states, state);
   for (int i = 0; i < taosArrayGetSize(t->insts); i++) {
-    uint32_t ip = *(int32_t *)taosArrayGet(t->insts, i);
-    sparSetAdd(cur, ip);
+    int32_t ip = *(int32_t *)taosArrayGet(t->insts, i);
+    bool    succ = sparSetAdd(cur, ip, NULL);
+    assert(succ == true);
   }
   dfaRun(builder->dfa, cur, next, byte);
 
@@ -126,7 +127,9 @@ bool dfaBuilderCachedState(FstDfaBuilder *builder, FstSparseSet *set, uint32_t *
   bool    isMatch = false;
 
   for (int i = 0; i < sparSetLen(set); i++) {
-    uint32_t ip = sparSetGet(set, i);
+    int32_t ip;
+
+    if (false == sparSetGet(set, i, &ip)) continue;
 
     Inst *inst = taosArrayGet(builder->dfa->insts, ip);
     if (inst->ty == JUMP || inst->ty == SPLIT) {
@@ -186,7 +189,8 @@ void dfaAdd(FstDfa *dfa, FstSparseSet *set, uint32_t ip) {
   if (sparSetContains(set, ip)) {
     return;
   }
-  sparSetAdd(set, ip);
+  bool succ = sparSetAdd(set, ip, NULL);
+  assert(succ == true);
   Inst *inst = taosArrayGet(dfa->insts, ip);
   if (inst->ty == MATCH || inst->ty == RANGE) {
     // do nothing
@@ -203,7 +207,8 @@ bool dfaRun(FstDfa *dfa, FstSparseSet *from, FstSparseSet *to, uint8_t byte) {
   bool isMatch = false;
   sparSetClear(to);
   for (int i = 0; i < sparSetLen(from); i++) {
-    uint32_t ip = sparSetGet(from, i);
+    int32_t ip;
+    if (false == sparSetGet(from, i, &ip)) continue;
 
     Inst *inst = taosArrayGet(dfa->insts, ip);
     if (inst->ty == JUMP || inst->ty == SPLIT) {
diff --git a/source/libs/index/src/indexFstSparse.c b/source/libs/index/src/indexFstSparse.c
index 71d8854dcc2a916240ea4f589c311e107c2b8c09..99ed5d6429c46e2d5b7fddd02c4be771345c9278 100644
--- a/source/libs/index/src/indexFstSparse.c
+++ b/source/libs/index/src/indexFstSparse.c
@@ -21,8 +21,12 @@ FstSparseSet *sparSetCreate(int32_t sz) {
     return NULL;
   }
 
-  ss->dense = (uint32_t *)taosMemoryCalloc(sz, sizeof(uint32_t));
-  ss->sparse = (uint32_t *)taosMemoryCalloc(sz, sizeof(uint32_t));
+  ss->dense = (int32_t *)taosMemoryMalloc(sz * sizeof(int32_t));
+  memset(ss->dense, -1, sz * sizeof(int32_t));
+  ss->sparse = (int32_t *)taosMemoryMalloc(sz * sizeof(int32_t));
+  memset(ss->sparse, -1, sz * sizeof(int32_t));
+  ss->cap = sz;
+
   ss->size = 0;
   return ss;
 }
@@ -38,23 +42,39 @@ uint32_t sparSetLen(FstSparseSet *ss) {
   // Get occupied size
   return ss == NULL ? 0 : ss->size;
 }
-uint32_t sparSetAdd(FstSparseSet *ss, uint32_t ip) {
+bool sparSetAdd(FstSparseSet *ss, int32_t ip, int32_t *idx) {
   if (ss == NULL) {
-    return 0;
+    return false;
+  }
+  if (ip >= ss->cap) {
+    return false;
   }
   uint32_t i = ss->size;
   ss->dense[i] = ip;
   ss->sparse[ip] = i;
   ss->size += 1;
-  return i;
+
+  if (idx != NULL) *idx = i;
+
+  return true;
 }
-uint32_t sparSetGet(FstSparseSet *ss, uint32_t i) {
-  // check later
-  return ss->dense[i];
+bool sparSetGet(FstSparseSet *ss, int32_t idx, int32_t *ip) {
+  if (idx >= ss->cap || idx >= ss->size) {
+    return false;
+  }
+  int32_t val = ss->dense[idx];
+  if (ip != NULL) {
+    *ip = val;
+  }
+  return val == -1 ? false : true;
 }
-bool sparSetContains(FstSparseSet *ss, uint32_t ip) {
-  uint32_t i = ss->sparse[ip];
-  if (i < ss->size && ss->dense[i] == ip) {
+bool sparSetContains(FstSparseSet *ss, int32_t ip) {
+  if (ip >= ss->cap) {
+    return false;
+  }
+  int32_t i = ss->sparse[ip];
+
+  if (i < ss->cap && i < ss->size && ss->dense[i] == ip) {
     return true;
   } else {
     return false;
@@ -64,5 +84,7 @@ void sparSetClear(FstSparseSet *ss) {
   if (ss == NULL) {
     return;
   }
+  memset(ss->dense, -1, ss->cap * sizeof(int32_t));
+  memset(ss->sparse, -1, ss->cap * sizeof(int32_t));
   ss->size = 0;
 }
diff --git a/source/libs/index/test/fstUtilUT.cc b/source/libs/index/test/fstUtilUT.cc
index 2c29758756704bafc0e650b04771af17bf57199e..22fe1a91503ab8799f7322c15b002e8a8ffdceed 100644
--- a/source/libs/index/test/fstUtilUT.cc
+++ b/source/libs/index/test/fstUtilUT.cc
@@ -51,10 +51,18 @@ class FstSparseSetEnv : public ::testing::Test {
 };
 
 // test FstDfaBuilder
-TEST_F(FstUtilEnv, test1) {}
-TEST_F(FstUtilEnv, test2) {}
-TEST_F(FstUtilEnv, test3) {}
-TEST_F(FstUtilEnv, test4) {}
+TEST_F(FstUtilEnv, test1) {
+  // test
+}
+TEST_F(FstUtilEnv, test2) {
+  // test
+}
+TEST_F(FstUtilEnv, test3) {
+  // test
+}
+TEST_F(FstUtilEnv, test4) {
+  // test
+}
 
 // test FstRegex
 
@@ -64,7 +72,38 @@ TEST_F(FstRegexEnv, test3) {}
 TEST_F(FstRegexEnv, test4) {}
 
 // test FstSparseSet
-TEST_F(FstSparseSetEnv, test1) {}
-TEST_F(FstSparseSetEnv, test2) {}
-TEST_F(FstSparseSetEnv, test3) {}
-TEST_F(FstSparseSetEnv, test4) {}
+TEST_F(FstSparseSetEnv, test1) {
+  for (int8_t i = 0; i < 20; i++) {
+    int32_t val = -1;
+    bool    succ = sparSetAdd(set, 'a' + i, &val);
+  }
+  EXPECT_EQ(sparSetLen(set), 20);
+  for (int8_t i = 0; i < 20; i++) {
+    int  val = -1;
+    bool find = sparSetGet(set, i, &val);
+    EXPECT_EQ(find, true);
+    EXPECT_EQ(val, i + 'a');
+  }
+  for (int8_t i = 'a'; i < 'a' + 20; i++) {
+    EXPECT_EQ(sparSetContains(set, i), true);
+  }
+
+  for (int8_t i = 'A'; i < 20; i++) {
+    EXPECT_EQ(sparSetContains(set, 'A'), false);
+  }
+
+  for (int i = 512; i < 1000; i++) {
+    EXPECT_EQ(sparSetAdd(set, i, NULL), false);
+
+    EXPECT_EQ(sparSetGet(set, i, NULL), false);
+    EXPECT_EQ(sparSetContains(set, i), false);
+  }
+  sparSetClear(set);
+
+  for (int i = 'a'; i < 'a' + 20; i++) {
+    EXPECT_EQ(sparSetGet(set, i, NULL), false);
+  }
+  for (int i = 1000; i < 2000; i++) {
+    EXPECT_EQ(sparSetGet(set, i, NULL), false);
+  }
+}