diff --git a/source/common/src/ttypes.c b/source/common/src/ttypes.c
index 3fd2ef8e730d64327f4a75448743f07248e49de3..b3999a49e7462e27582907b4f12aef1b24e2b35c 100644
--- a/source/common/src/ttypes.c
+++ b/source/common/src/ttypes.c
@@ -402,7 +402,8 @@ tDataTypeDescriptor tDataTypes[TSDB_DATA_TYPE_MAX] = {
     {TSDB_DATA_TYPE_UINT, 12, INT_BYTES, "INT UNSIGNED", 0, UINT32_MAX, tsCompressInt, tsDecompressInt, getStatics_u32},
     {TSDB_DATA_TYPE_UBIGINT, 15, LONG_BYTES, "BIGINT UNSIGNED", 0, UINT64_MAX, tsCompressBigint, tsDecompressBigint,
      getStatics_u64},
-    {TSDB_DATA_TYPE_JSON, 4, TSDB_MAX_JSON_TAG_LEN, "JSON", 0, 0, tsCompressString, tsDecompressString, getStatics_nchr},
+    {TSDB_DATA_TYPE_JSON, 4, TSDB_MAX_JSON_TAG_LEN, "JSON", 0, 0, tsCompressString, tsDecompressString,
+     getStatics_nchr},
 };
 
 char tTokenTypeSwitcher[13] = {
diff --git a/source/dnode/vnode/src/inc/meta.h b/source/dnode/vnode/src/inc/meta.h
index f1917d5fea02f126850495aed62496aa62f7f1a0..60b3a889ef0b7702c551ccb667432b7e41a00d43 100644
--- a/source/dnode/vnode/src/inc/meta.h
+++ b/source/dnode/vnode/src/inc/meta.h
@@ -96,8 +96,10 @@ typedef struct {
 #pragma pack(push, 1)
 typedef struct {
   tb_uid_t suid;
-  int16_t  cid;
-  char     data[];
+  int32_t  cid;
+  uint8_t  isNull : 1;
+  uint8_t  type : 7;
+  uint8_t  data[];  // val + uid
 } STagIdxKey;
 #pragma pack(pop)
 
diff --git a/source/dnode/vnode/src/meta/metaOpen.c b/source/dnode/vnode/src/meta/metaOpen.c
index 8b3f555f4fa0a78bfeea2bc2a70d66c87787934b..07422e3193b6f77c252ea6442d14923d14a56242 100644
--- a/source/dnode/vnode/src/meta/metaOpen.c
+++ b/source/dnode/vnode/src/meta/metaOpen.c
@@ -227,8 +227,7 @@ static int ctbIdxKeyCmpr(const void *pKey1, int kLen1, const void *pKey2, int kL
 static int tagIdxKeyCmpr(const void *pKey1, int kLen1, const void *pKey2, int kLen2) {
   STagIdxKey *pTagIdxKey1 = (STagIdxKey *)pKey1;
   STagIdxKey *pTagIdxKey2 = (STagIdxKey *)pKey2;
-  int8_t     *p1, *p2;
-  int8_t      type;
+  tb_uid_t    uid1, uid2;
   int         c;
 
   // compare suid
@@ -245,31 +244,34 @@ static int tagIdxKeyCmpr(const void *pKey1, int kLen1, const void *pKey2, int kL
     return -1;
   }
 
-  // compare value
-  p1 = pTagIdxKey1->data;
-  p2 = pTagIdxKey2->data;
-  ASSERT(p1[0] == p2[0]);
-  type = p1[0];
+  ASSERT(pTagIdxKey1->type == pTagIdxKey2->type);
 
-  p1++;
-  p2++;
-
-  c = doCompare(p1, p2, type, 0);
-  if (c) return c;
-
-  if (IS_VAR_DATA_TYPE(type)) {
-    p1 = p1 + varDataTLen(p1);
-    p2 = p2 + varDataTLen(p2);
-  } else {
-    p1 = p1 + tDataTypes[type].bytes;
-    p2 = p2 + tDataTypes[type].bytes;
+  // check NULL, NULL is always the smallest
+  if (pTagIdxKey1->isNull && !pTagIdxKey2->isNull) {
+    return -1;
+  } else if (!pTagIdxKey1->isNull && pTagIdxKey2->isNull) {
+    return 1;
+  } else if (!pTagIdxKey1->isNull && !pTagIdxKey2->isNull) {
+    // all not NULL, compr tag vals
+    c = doCompare(pTagIdxKey1->data, pTagIdxKey2->data, pTagIdxKey1->type, 0);
+    if (c) return c;
+
+    if (IS_VAR_DATA_TYPE(pTagIdxKey1->type)) {
+      uid1 = *(tb_uid_t *)(pTagIdxKey1->data + varDataTLen(pTagIdxKey1->data));
+      uid2 = *(tb_uid_t *)(pTagIdxKey2->data + varDataTLen(pTagIdxKey2->data));
+    } else {
+      uid1 = *(tb_uid_t *)(pTagIdxKey1->data + tDataTypes[pTagIdxKey1->type].bytes);
+      uid2 = *(tb_uid_t *)(pTagIdxKey2->data + tDataTypes[pTagIdxKey2->type].bytes);
+    }
   }
 
-  // compare suid
-  if (*(tb_uid_t *)p1 > *(tb_uid_t *)p2) {
-    return 1;
-  } else if (*(tb_uid_t *)p1 < *(tb_uid_t *)p2) {
+  // compare uid
+  if (uid1 < uid2) {
     return -1;
+  } else if (uid1 > uid2) {
+    return 1;
+  } else {
+    return 0;
   }
 
   return 0;
diff --git a/source/dnode/vnode/src/meta/metaTable.c b/source/dnode/vnode/src/meta/metaTable.c
index 20248f39fb26c33bcef9e336d46493f10a7f9336..d666bd22c1ead949a1a3e4f4e466051fb34d8530 100644
--- a/source/dnode/vnode/src/meta/metaTable.c
+++ b/source/dnode/vnode/src/meta/metaTable.c
@@ -22,7 +22,7 @@ static int metaUpdateNameIdx(SMeta *pMeta, const SMetaEntry *pME);
 static int metaUpdateTtlIdx(SMeta *pMeta, const SMetaEntry *pME);
 static int metaSaveToSkmDb(SMeta *pMeta, const SMetaEntry *pME);
 static int metaUpdateCtbIdx(SMeta *pMeta, const SMetaEntry *pME);
-static int metaUpdateTagIdx(SMeta *pMeta, const SMetaEntry *pME);
+static int metaUpdateTagIdx(SMeta *pMeta, const SMetaEntry *pCtbEntry);
 
 int metaCreateSTable(SMeta *pMeta, int64_t version, SVCreateStbReq *pReq) {
   SMetaEntry  me = {0};
@@ -389,8 +389,73 @@ static int metaUpdateCtbIdx(SMeta *pMeta, const SMetaEntry *pME) {
   return tdbDbInsert(pMeta->pCtbIdx, &ctbIdxKey, sizeof(ctbIdxKey), NULL, 0, &pMeta->txn);
 }
 
-static int metaUpdateTagIdx(SMeta *pMeta, const SMetaEntry *pME) {
-  // TODO
+static int metaCreateTagIdxKey(tb_uid_t suid, int32_t cid, const void *pTagData, int8_t type, tb_uid_t uid,
+                               STagIdxKey **ppTagIdxKey, int32_t *nTagIdxKey) {
+  int32_t nTagData = 0;
+
+  if (pTagData) {
+    if (IS_VAR_DATA_TYPE(type)) {
+      nTagData = varDataTLen(pTagData);
+    } else {
+      nTagData = tDataTypes[type].bytes;
+    }
+  }
+  *nTagIdxKey = sizeof(STagIdxKey) + nTagData + sizeof(tb_uid_t);
+
+  *ppTagIdxKey = (STagIdxKey *)taosMemoryMalloc(*nTagIdxKey);
+  if (*ppTagIdxKey == NULL) {
+    terrno = TSDB_CODE_OUT_OF_MEMORY;
+    return -1;
+  }
+
+  (*ppTagIdxKey)->suid = suid;
+  (*ppTagIdxKey)->cid = cid;
+  (*ppTagIdxKey)->isNull = (pTagData == NULL) ? 1 : 0;
+  (*ppTagIdxKey)->type = type;
+  if (nTagData) memcpy((*ppTagIdxKey)->data, pTagData, nTagData);
+  *(tb_uid_t *)((*ppTagIdxKey)->data + nTagData) = uid;
+
+  return 0;
+}
+
+static void metaDestroyTagIdxKey(STagIdxKey *pTagIdxKey) {
+  if (pTagIdxKey) taosMemoryFree(pTagIdxKey);
+}
+
+static int metaUpdateTagIdx(SMeta *pMeta, const SMetaEntry *pCtbEntry) {
+  void          *pData = NULL;
+  int            nData = 0;
+  STbDbKey       tbDbKey = {0};
+  SMetaEntry     stbEntry = {0};
+  STagIdxKey    *pTagIdxKey = NULL;
+  int32_t        nTagIdxKey;
+  const SSchema *pTagColumn;       // = &stbEntry.stbEntry.schema.pSchema[0];
+  const void    *pTagData = NULL;  //
+  SDecoder       dc = {0};
+
+  // get super table
+  tdbDbGet(pMeta->pUidIdx, &pCtbEntry->ctbEntry.suid, sizeof(tb_uid_t), &pData, &nData);
+  tbDbKey.uid = pCtbEntry->ctbEntry.suid;
+  tbDbKey.version = *(int64_t *)pData;
+  tdbDbGet(pMeta->pTbDb, &tbDbKey, sizeof(tbDbKey), &pData, &nData);
+
+  tDecoderInit(&dc, pData, nData);
+  metaDecodeEntry(&dc, &stbEntry);
+
+  pTagColumn = &stbEntry.stbEntry.schemaTag.pSchema[0];
+  pTagData = tdGetKVRowValOfCol((const SKVRow)pCtbEntry->ctbEntry.pTags, pTagColumn->colId);
+
+  // update tag index
+  if (metaCreateTagIdxKey(pCtbEntry->ctbEntry.suid, pTagColumn->colId, pTagData, pTagColumn->type, pCtbEntry->uid,
+                          &pTagIdxKey, &nTagIdxKey) < 0) {
+    return -1;
+  }
+  tdbDbInsert(pMeta->pTagIdx, pTagIdxKey, nTagIdxKey, NULL, 0, &pMeta->txn);
+  metaDestroyTagIdxKey(pTagIdxKey);
+
+  tDecoderClear(&dc);
+  tdbFree(pData);
+
   return 0;
 }