diff --git a/source/libs/index/inc/index_fst.h b/source/libs/index/inc/index_fst.h
index 7ab9358cd15a33b051f67b0b17eb599491fab42d..37feb79ac809529b853b65e641a01fb65e1bd830 100644
--- a/source/libs/index/inc/index_fst.h
+++ b/source/libs/index/inc/index_fst.h
@@ -80,6 +80,9 @@ void fstBuilderInsertOutput(FstBuilder *b, FstSlice bs, Output in);
 OrderType fstBuilderCheckLastKey(FstBuilder *b, FstSlice bs, bool ckDup);
 void fstBuilderCompileFrom(FstBuilder *b, uint64_t istate);
 CompiledAddr fstBuilderCompile(FstBuilder *b, FstBuilderNode *bn);
+void* fstBuilerIntoInner(FstBuilder *b);
+void  fstBuilderFinish(FstBuilder *b); 
+
 
 
 
@@ -216,6 +219,15 @@ bool fstNodeFindInput(FstNode *node, uint8_t b, uint64_t *res);
 bool fstNodeCompile(FstNode *node, void *w, CompiledAddr lastAddr, CompiledAddr addr, FstBuilderNode *builderNode); 
 FstSlice  fstNodeAsSlice(FstNode *node); 
 
+// ops  
+
+typedef struct FstIndexedValue {
+  uint64_t index;
+  uint64_t value;
+} FstIndexedValue;
+
+FstLastTransition *fstLastTransitionCreate(uint8_t inp, Output out);
+void fstLastTransitionDestroy(FstLastTransition *trn);
 
 
 typedef struct FstMeta {
@@ -227,20 +239,20 @@ typedef struct FstMeta {
 } FstMeta;
 
 typedef struct Fst {
-  FstMeta meta; 
-  void    *data;  //  
+  FstMeta  *meta; 
+  FstSlice *data;  //  
+  FstNode  *root;  // 
 } Fst;
 
-// ops  
-
-typedef struct FstIndexedValue {
-  uint64_t index;
-  uint64_t value;
-} FstIndexedValue;
-
-FstLastTransition *fstLastTransitionCreate(uint8_t inp, Output out);
-void fstLastTransitionDestroy(FstLastTransition *trn);
-
+// refactor simple function 
 
+Fst*         fstCreate(FstSlice *data);
+void         fstDestroy(Fst *fst);
 
+bool         fstGet(Fst *fst, FstSlice *b, Output *out);
+FstNode*     fstGetNode(Fst *fst, CompiledAddr); 
+FstType      fstGetType(Fst *fst); 
+CompiledAddr fstGetRootAddr(Fst *fst);
+Output fstEmptyFinalOutput(Fst *fst, bool *null);
+bool fstVerify(Fst *fst);
 #endif
diff --git a/source/libs/index/inc/index_fst_counting_writer.h b/source/libs/index/inc/index_fst_counting_writer.h
index fbb2f1cff7b643c710e0d2f551e7d2a2c05b543b..465080403482c6022900eed2e3a4fe98aecb30de 100644
--- a/source/libs/index/inc/index_fst_counting_writer.h
+++ b/source/libs/index/inc/index_fst_counting_writer.h
@@ -27,9 +27,11 @@ typedef struct FstCountingWriter {
 
 uint64_t fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t bufLen); 
 
-int FstCountingWriterFlush(FstCountingWriter *write);
+int fstCountingWriterFlush(FstCountingWriter *write);
 
 
+uint32_t fstCountingWriterMaskedCheckSum(FstCountingWriter *write);
+
 FstCountingWriter *fstCountingWriterCreate(void *wtr);
 void fstCountingWriterDestroy(FstCountingWriter *w); 
 
diff --git a/source/libs/index/inc/index_fst_util.h b/source/libs/index/inc/index_fst_util.h
index 5b84632418b6f11e70ef6bc1233b89d944e8ce2c..ff0946063d011bb3df9ed290dffff8c120a48055 100644
--- a/source/libs/index/inc/index_fst_util.h
+++ b/source/libs/index/inc/index_fst_util.h
@@ -32,9 +32,9 @@ extern const CompiledAddr EMPTY_ADDRESS;
 extern const CompiledAddr NONE_ADDRESS;
 
 // This version number is written to every finite state transducer created by
-// this crate. When a finite state transducer is read, its version number is
+// this version When a finite state transducer is read, its version number is
 // checked against this value.
-extern const uint64_t    version;
+extern const uint64_t    VERSION;
 // The threshold (in number of transitions) at which an index is created for                                   
 // a node's transitions. This speeds up lookup time at the expense of FST size 
 
diff --git a/source/libs/index/src/index_fst.c b/source/libs/index/src/index_fst.c
index 8b9aa22fc689adb48887cdc493c69ffb266b769b..6c1ea8cfebcccdd2a7013a4c161caaee96ff8b27 100644
--- a/source/libs/index/src/index_fst.c
+++ b/source/libs/index/src/index_fst.c
@@ -14,7 +14,8 @@
  */
 
 #include "index_fst.h"
-
+#include "tcoding.h"
+#include "tchecksum.h"
 
 
 static void fstPackDeltaIn(FstCountingWriter *wrt, CompiledAddr nodeAddr, CompiledAddr transAddr, uint8_t nBytes) {
@@ -98,7 +99,7 @@ void fstUnFinishedNodesAddSuffix(FstUnFinishedNodes *nodes, FstSlice bs, Output
   FstBuilderNodeUnfinished *un = taosArrayGet(nodes->stack, sz);
   assert(un->last == NULL);
 
-  
+     
   
   //FstLastTransition *trn = malloc(sizeof(FstLastTransition)); 
   //trn->inp = s->data[s->start]; 
@@ -146,24 +147,27 @@ uint64_t fstUnFinishedNodesFindCommPrefixAndSetOutput(FstUnFinishedNodes *node,
   size_t lsz = (size_t)(s->end - s->start + 1);          // data len 
   size_t ssz = taosArrayGetSize(node->stack);  // stack size
 
-  uint64_t res = 0;
-  for (size_t i = 0; i < lsz && i < ssz; i++) {
+  uint64_t i = 0;
+  for (i = 0; i < lsz && i < ssz; i++) {
     FstBuilderNodeUnfinished *un = taosArrayGet(node->stack, i);
 
-    FstLastTransition *last = un->last; 
-    if (last->inp == s->data[s->start + i]) {
-      uint64_t commPrefix = last->out;      
-      uint64_t addPrefix  = last->out - commPrefix; 
-      out = out - commPrefix; 
-      last->out = commPrefix;
-      if (addPrefix != 0) {
-        fstBuilderNodeUnfinishedAddOutputPrefix(un, addPrefix);  
-      }
+    FstLastTransition *t = un->last; 
+    uint64_t addPrefix = 0;  
+    if (t && t->inp == s->data[s->start + i]) {
+      uint64_t commPrefix = MIN(t->out, *out);      
+      uint64_t tAddPrefix  = t->out - commPrefix; 
+      (*out) = (*out) - commPrefix; 
+      t->out = commPrefix;
+      addPrefix = tAddPrefix; 
     } else {
-      break;
+       break;
+    }
+    if (addPrefix != 0) {
+      fstBuilderNodeUnfinishedAddOutputPrefix(un, addPrefix);  
+
     }
   }   
-  return res;
+  return i;
 } 
 
 
@@ -771,16 +775,16 @@ void fstBuilderInsertOutput(FstBuilder *b, FstSlice bs, Output in) {
      return;
    }
    Output out; 
-   uint64_t prefixLen;
-   if (in != 0) { //if let Some(in) = in 
-      prefixLen = fstUnFinishedNodesFindCommPrefixAndSetOutput(b->unfinished, bs, in, &out);  
-   } else {
-      prefixLen = fstUnFinishedNodesFindCommPrefix(b->unfinished, bs);
-      out = 0;
-   }
-
+   //if (in != 0) { //if let Some(in) = in 
+   //   prefixLen = fstUnFinishedNodesFindCommPrefixAndSetOutput(b->unfinished, bs, in, &out);  
+   //} else {
+   //   prefixLen = fstUnFinishedNodesFindCommPrefix(b->unfinished, bs);
+   //   out = 0;
+   //}
+   uint64_t prefixLen = fstUnFinishedNodesFindCommPrefixAndSetOutput(b->unfinished, bs, in, &out);
+  
    if (prefixLen == FST_SLICE_LEN(s)) {
-      assert(out != 0);
+      assert(out == 0);
       return;
    }
 
@@ -849,6 +853,31 @@ CompiledAddr fstBuilderCompile(FstBuilder *b, FstBuilderNode *bn) {
   return b->lastAddr;  
 }
 
+void* fstBuilderInsertInner(FstBuilder *b) {
+  fstBuilderCompileFrom(b, 0);  
+  FstBuilderNode *rootNode = fstUnFinishedNodesPopRoot(b->unfinished); 
+  CompiledAddr  rootAddr = fstBuilderCompile(b, rootNode);
+
+  uint8_t buf64[8] = {0}; 
+
+  taosEncodeFixedU64((void **)&buf64, b->len); 
+  fstCountingWriterWrite(b->wrt, buf64, sizeof(buf64));  
+    
+  taosEncodeFixedU64((void **)&buf64, rootAddr);  
+  fstCountingWriterWrite(b->wrt, buf64, sizeof(buf64));  
+
+  uint8_t buf32[4] = {0};
+  uint32_t sum = fstCountingWriterMaskedCheckSum(b->wrt);
+  taosEncodeFixedU32((void **)&buf32, sum); 
+  fstCountingWriterWrite(b->wrt, buf32, sizeof(buf32));  
+  
+  fstCountingWriterFlush(b->wrt);
+  return b->wrt;
+  
+}
+void fstBuilderFinish(FstBuilder *b) {
+  fstBuilderInsertInner(b);
+}
 
 
 
@@ -894,4 +923,108 @@ void fstBuilderNodeUnfinishedAddOutputPrefix(FstBuilderNodeUnfinished *unNode, O
   return;
 }
 
+Fst* fstCreate(FstSlice *slice) {
+  char *buf = slice->data;
+  uint64_t skip = 0;  
+  uint64_t len = slice->dLen;
+  if (len < 36) { 
+    return NULL; 
+  }
+
+  uint64_t version; 
+  taosDecodeFixedU64(buf, &version); 
+  skip += sizeof(version); 
+  if (version == 0 || version > VERSION) {
+    return NULL; 
+  }  
+
+  uint64_t type;
+  taosDecodeFixedU64(buf + skip, &type);
+  skip += sizeof(type); 
+
+  uint32_t checkSum = 0;
+  len -= sizeof(checkSum);
+  taosDecodeFixedU32(buf + len, &checkSum); 
+
+  CompiledAddr rootAddr;
+  len -= sizeof(rootAddr); 
+  taosDecodeFixedU64(buf + len, &rootAddr); 
+
+  uint64_t fstLen; 
+  len -= sizeof(fstLen); 
+  taosDecodeFixedU64(buf + len, &fstLen);
+  //TODO(validat root addr)
+  // 
+  Fst *fst= (Fst *)calloc(1, sizeof(Fst)); 
+  if (fst == NULL) { return NULL; }  
+  
+  fst->meta = (FstMeta *)malloc(sizeof(FstMeta));
+  if (NULL == fst->meta) { 
+    goto FST_CREAT_FAILED; 
+  }
+
+  fst->meta->version   = version;  
+  fst->meta->rootAddr = rootAddr; 
+  fst->meta->ty       = type;
+  fst->meta->len      = fstLen;
+  fst->meta->checkSum = checkSum;
+  fst->data = slice; 
+  return fst;
+
+FST_CREAT_FAILED: 
+  free(fst->meta); 
+  free(fst);
+
+}
+void fstDestroy(Fst *fst) {
+  if (fst) { 
+    free(fst->meta); 
+    fstNodeDestroy(fst->root);  
+  } 
+  free(fst); 
+}
+
+bool fstGet(Fst *fst, FstSlice *b, Output *out) {
+   
+  return false; 
+}
+
+FstNode* fstGetNode(Fst *fst, CompiledAddr addr) {
+  if (fst->root != NULL) {
+    return fst->root;
+  }
+  fst->root = fstNodeCreate(fst->meta->version, addr, fst->data); 
+  return fst->root;
+  
+}
+FstType fstGetType(Fst *fst) {
+  return fst->meta->ty;
+}
+CompiledAddr fstGetRootAddr(Fst *fst) {
+  return fst->meta->rootAddr;
+} 
+
+Output fstEmptyFinalOutput(Fst *fst, bool *null) {
+  Output res = 0;
+  FstNode *node = fst->root;
+  if (FST_NODE_IS_FINAL(node)) {
+    *null = false;
+    res = FST_NODE_FINAL_OUTPUT(node); 
+  } else {
+    *null = true;
+  }
+  return res;
+}
+
+
+bool fstVerify(Fst *fst) {
+  uint32_t checkSum = fst->meta->checkSum;
+  FstSlice *data    = fst->data;          
+  TSCKSUM initSum  = 0;  
+  if (taosCheckChecksumWhole(data->data, data->dLen)) {
+    return false;
+  }
+  
+}
+
 
diff --git a/source/libs/index/src/index_fst_counting_writer.c b/source/libs/index/src/index_fst_counting_writer.c
index b253db986a1612fc1322e9d049bd9690a401a5d1..a0a2c380f170724984dae7bc9e12864d4ce16f24 100644
--- a/source/libs/index/src/index_fst_counting_writer.c
+++ b/source/libs/index/src/index_fst_counting_writer.c
@@ -37,6 +37,9 @@ uint64_t fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t
   return bufLen; 
 } 
 
+uint32_t fstCountingWriterMaskedCheckSum(FstCountingWriter *write) {
+  return 0;
+}
 int fstCountingWriterFlush(FstCountingWriter *write) {
   //write->wtr->flush
   return 1;
diff --git a/source/libs/index/src/index_fst_util.c b/source/libs/index/src/index_fst_util.c
index c4499f8e0d86d04097024dbbabf0edc6f0aca617..94bf650acd8037e63a5486ce83d8562b09e1f7fd 100644
--- a/source/libs/index/src/index_fst_util.c
+++ b/source/libs/index/src/index_fst_util.c
@@ -25,7 +25,7 @@ const CompiledAddr NONE_ADDRESS   = 1;
 // This version number is written to every finite state transducer created by
 // this crate. When a finite state transducer is read, its version number is
 // checked against this value.
-const uint64_t    version        = 3;
+const uint64_t    VERSION        = 3;
 // The threshold (in number of transitions) at which an index is created for                                   
 // a node's transitions. This speeds up lookup time at the expense of FST size