diff --git a/source/libs/index/inc/index_fst.h b/source/libs/index/inc/index_fst.h
index 1230fe17ff..04e9b8b4ac 100644
--- a/source/libs/index/inc/index_fst.h
+++ b/source/libs/index/inc/index_fst.h
@@ -20,6 +20,7 @@
 #include "tarray.h"
 #include "index_fst_util.h"
 #include "index_fst_registry.h"
+#include "index_fst_counting_writer.h"
 
 
 typedef struct FstNode FstNode;
@@ -35,7 +36,6 @@ typedef struct FstRange {
 typedef enum { OneTransNext, OneTrans, AnyTrans, EmptyFinal} State;
 typedef enum { Included, Excluded, Unbounded} FstBound; 
 
-typedef uint32_t CheckSummer;
 
 
 /*
@@ -60,11 +60,6 @@ void fstUnFinishedNodesAddSuffix(FstUnFinishedNodes *node, FstSlice bs, Output o
 uint64_t fstUnFinishedNodesFindCommPrefix(FstUnFinishedNodes *node, FstSlice bs);
 uint64_t FstUnFinishedNodesFindCommPreifxAndSetOutput(FstUnFinishedNodes *node, FstSlice bs, Output in, Output *out);
 
-typedef struct FstCountingWriter {
-  void*    wtr;  // wrap any writer that counts and checksum bytes written 
-  uint64_t count; 
-  CheckSummer summer;  
-} FstCountingWriter;
 
 typedef struct FstBuilder {
   FstCountingWriter  wtr;         // The FST raw data is written directly to `wtr`.  
diff --git a/source/libs/index/src/index_fst.c b/source/libs/index/src/index_fst.c
index 2974e7f9b5..cf8a6eabfe 100644
--- a/source/libs/index/src/index_fst.c
+++ b/source/libs/index/src/index_fst.c
@@ -275,8 +275,6 @@ bool fstNodeCompile(FstNode *node, void *w, CompiledAddr lastAddr, CompiledAddr
 } 
 
 
-
-
 FstBuilder *fstBuilderCreate(void *w, FstType ty) {
   FstBuilder *b = malloc(sizeof(FstBuilder));  
   if (NULL == b) { return b; }
diff --git a/source/libs/index/src/index_fst_node.c b/source/libs/index/src/index_fst_node.c
index 23af4a4a4b..d7aa1e5041 100644
--- a/source/libs/index/src/index_fst_node.c
+++ b/source/libs/index/src/index_fst_node.c
@@ -26,14 +26,13 @@ FstBuilderNode *fstBuilderNodeClone(FstBuilderNode *src) {
   FstBuilderNode *node = malloc(sizeof(FstBuilderNode));  
   if (node == NULL) { return NULL; }
 
-      
+  // 
   size_t sz = taosArrayGetSize(src->trans);
   SArray *trans = taosArrayInit(sz, sizeof(FstTransition));
 
   for (size_t i = 0; i < sz; i++) {
     FstTransition *tran = taosArrayGet(src->trans, i);
-    FstTransition t = *tran;
-    taosArrayPush(trans, &t);   
+    taosArrayPush(trans, tran);   
   }
 
   node->trans = trans; 
@@ -47,9 +46,11 @@ void fstBuilderNodeCloneFrom(FstBuilderNode *dst, FstBuilderNode *src) {
   if (dst == NULL || src == NULL) { return; } 
 
   dst->isFinal     = src->isFinal;
-  dst->finalOutput = src->finalOutput ;
-  dst->trans       = src->trans;    
+  dst->finalOutput = src->finalOutput;
 
+  // avoid mem leak
+  taosArrayDestroy(dst->trans); 
+  dst->trans       = src->trans;    
   src->trans = NULL;
 }
 
diff --git a/source/libs/index/src/index_fst_registry.c b/source/libs/index/src/index_fst_registry.c
index 5d6c7b1712..718832c803 100644
--- a/source/libs/index/src/index_fst_registry.c
+++ b/source/libs/index/src/index_fst_registry.c
@@ -32,6 +32,7 @@ uint64_t fstRegistryHash(FstRegistry *registry, FstBuilderNode *bNode) {
     h = (h ^ (uint64_t)(trn->addr))* FNV_PRIME;
   } 
   return h %(registry->tableSize); 
+
 }
 static void fstRegistryCellSwap(SArray *arr, uint32_t a, uint32_t b) {
   size_t sz = taosArrayGetSize(arr);
@@ -72,10 +73,14 @@ FstRegistry* fstRegistryCreate(uint64_t tableSize, uint64_t mruSize) {
 
   uint64_t nCells = tableSize * mruSize; 
   SArray* tb = (SArray *)taosArrayInit(nCells, sizeof(FstRegistryCell)); 
+  if (NULL == tb) { 
+    free(registry); 
+    return NULL; 
+  }
+
   for (uint64_t i = 0; i < nCells; i++) {
-    FstRegistryCell *cell = taosArrayGet(tb, i);
-    cell->addr = NONE_ADDRESS; 
-    cell->node = fstBuilderNodeDefault(); 
+    FstRegistryCell cell = {.addr = NONE_ADDRESS, .node = fstBuilderNodeDefault()}; 
+    taosArrayPush(tb, &cell);  
   }
   
   registry->table = tb;   
@@ -98,11 +103,9 @@ FstRegistryEntry *fstRegistryGetEntry(FstRegistry *registry, FstBuilderNode *bNo
     //cell->isNode && 
     if (cell->addr != NONE_ADDRESS && cell->node == bNode) {
        entry->state = FOUND;
-       entry->addr =  cell->addr ;
+       entry->addr  = cell->addr ;
        return entry; 
     } else {
-       // clone from bNode, refactor later
-       //
        fstBuilderNodeCloneFrom(cell->node, bNode);
        entry->state = NOTFOUND;
        entry->cell  = cell; // copy or not