diff --git a/include/common/tmsg.h b/include/common/tmsg.h
index 857a554f62..2a29d9b7c7 100644
--- a/include/common/tmsg.h
+++ b/include/common/tmsg.h
@@ -1817,6 +1817,8 @@ typedef struct SVCreateTbReq {
   tb_uid_t uid;
   int64_t  ctime;
   int32_t  ttl;
+  int32_t  commentLen;
+  char*    comment;
   int8_t   type;
   union {
     struct {
@@ -1834,6 +1836,7 @@ int tDecodeSVCreateTbReq(SDecoder* pCoder, SVCreateTbReq* pReq);
 
 static FORCE_INLINE void tdDestroySVCreateTbReq(SVCreateTbReq* req) {
   taosMemoryFreeClear(req->name);
+  taosMemoryFreeClear(req->comment);
   if (req->type == TSDB_CHILD_TABLE) {
     taosMemoryFreeClear(req->ctb.pTag);
   } else if (req->type == TSDB_NORMAL_TABLE) {
@@ -1930,7 +1933,7 @@ typedef struct {
   // TSDB_ALTER_TABLE_UPDATE_OPTIONS
   int8_t  updateTTL;
   int32_t newTTL;
-  int8_t  updateComment;
+  int32_t newCommentLen;
   char*   newComment;
 } SVAlterTbReq;
 
diff --git a/include/common/tmsgdef.h b/include/common/tmsgdef.h
index f89f548fc5..1b640642d7 100644
--- a/include/common/tmsgdef.h
+++ b/include/common/tmsgdef.h
@@ -198,7 +198,7 @@ enum {
   TD_DEF_MSG_TYPE(TDMT_VND_ALTER_CONFIRM, "alter-confirm", NULL, NULL)
   TD_DEF_MSG_TYPE(TDMT_VND_ALTER_HASHRANGE, "alter-hashrange", NULL, NULL)
   TD_DEF_MSG_TYPE(TDMT_VND_COMPACT, "compact", NULL, NULL)
-
+  TD_DEF_MSG_TYPE(TDMT_VND_DROP_TTL_TABLE, "drop-ttl-stb", NULL, NULL)
   TD_NEW_MSG_SEG(TDMT_QND_MSG)
 
   //shared by snode and vnode
diff --git a/include/libs/nodes/cmdnodes.h b/include/libs/nodes/cmdnodes.h
index cae20499a3..13a8dbd7e3 100644
--- a/include/libs/nodes/cmdnodes.h
+++ b/include/libs/nodes/cmdnodes.h
@@ -87,6 +87,7 @@ typedef struct SAlterDatabaseStmt {
 
 typedef struct STableOptions {
   ENodeType  type;
+  bool       commentNull;
   char       comment[TSDB_TB_COMMENT_LEN];
   SNodeList* pMaxDelay;
   int64_t    maxDelay1;
@@ -126,6 +127,7 @@ typedef struct SCreateSubTableClause {
   bool       ignoreExists;
   SNodeList* pSpecificTags;
   SNodeList* pValsOfTags;
+  STableOptions* pOptions;
 } SCreateSubTableClause;
 
 typedef struct SCreateMultiTableStmt {
diff --git a/source/common/src/systable.c b/source/common/src/systable.c
index a1b64b363c..e7b6342150 100644
--- a/source/common/src/systable.c
+++ b/source/common/src/systable.c
@@ -124,7 +124,7 @@ static const SSysDbTableSchema userStbsSchema[] = {
     {.name = "columns", .bytes = 4, .type = TSDB_DATA_TYPE_INT},
     {.name = "tags", .bytes = 4, .type = TSDB_DATA_TYPE_INT},
     {.name = "last_update", .bytes = 8, .type = TSDB_DATA_TYPE_TIMESTAMP},
-    {.name = "table_comment", .bytes = 1024 + VARSTR_HEADER_SIZE, .type = TSDB_DATA_TYPE_VARCHAR},
+    {.name = "table_comment", .bytes = TSDB_TB_COMMENT_LEN + VARSTR_HEADER_SIZE, .type = TSDB_DATA_TYPE_VARCHAR},
 };
 
 static const SSysDbTableSchema streamSchema[] = {
@@ -148,7 +148,7 @@ static const SSysDbTableSchema userTblsSchema[] = {
     {.name = "uid", .bytes = 8, .type = TSDB_DATA_TYPE_BIGINT},
     {.name = "vgroup_id", .bytes = 4, .type = TSDB_DATA_TYPE_INT},
     {.name = "ttl", .bytes = 4, .type = TSDB_DATA_TYPE_INT},
-    {.name = "table_comment", .bytes = 512 + VARSTR_HEADER_SIZE, .type = TSDB_DATA_TYPE_VARCHAR},
+    {.name = "table_comment", .bytes = TSDB_TB_COMMENT_LEN + VARSTR_HEADER_SIZE, .type = TSDB_DATA_TYPE_VARCHAR},
     {.name = "type", .bytes = 20 + VARSTR_HEADER_SIZE, .type = TSDB_DATA_TYPE_VARCHAR},
 };
 
diff --git a/source/common/src/tmsg.c b/source/common/src/tmsg.c
index 2443ffbb7f..c3c96972b7 100644
--- a/source/common/src/tmsg.c
+++ b/source/common/src/tmsg.c
@@ -524,7 +524,7 @@ int32_t tSerializeSMCreateStbReq(void *buf, int32_t bufLen, SMCreateStbReq *pReq
   }
 
   if (pReq->commentLen > 0) {
-    if (tEncodeBinary(&encoder, pReq->comment, pReq->commentLen) < 0) return -1;
+    if (tEncodeCStr(&encoder, pReq->comment) < 0) return -1;
   }
   if (pReq->ast1Len > 0) {
     if (tEncodeBinary(&encoder, pReq->pAst1, pReq->ast1Len) < 0) return -1;
@@ -589,7 +589,7 @@ int32_t tDeserializeSMCreateStbReq(void *buf, int32_t bufLen, SMCreateStbReq *pR
   }
 
   if (pReq->commentLen > 0) {
-    pReq->comment = taosMemoryMalloc(pReq->commentLen);
+    pReq->comment = taosMemoryMalloc(pReq->commentLen + 1);
     if (pReq->comment == NULL) return -1;
     if (tDecodeCStrTo(&decoder, pReq->comment) < 0) return -1;
   }
@@ -707,7 +707,7 @@ int32_t tDeserializeSMAlterStbReq(void *buf, int32_t bufLen, SMAlterStbReq *pReq
   if (tDecodeI32(&decoder, &pReq->ttl) < 0) return -1;
   if (tDecodeI32(&decoder, &pReq->commentLen) < 0) return -1;
   if (pReq->commentLen > 0) {
-    pReq->comment = taosMemoryMalloc(pReq->commentLen);
+    pReq->comment = taosMemoryMalloc(pReq->commentLen + 1);
     if (pReq->comment == NULL) return -1;
     if (tDecodeCStrTo(&decoder, pReq->comment) < 0) return -1;
   }
@@ -4374,6 +4374,10 @@ int tEncodeSVCreateTbReq(SEncoder *pCoder, const SVCreateTbReq *pReq) {
   if (tEncodeI64(pCoder, pReq->ctime) < 0) return -1;
   if (tEncodeI32(pCoder, pReq->ttl) < 0) return -1;
   if (tEncodeI8(pCoder, pReq->type) < 0) return -1;
+  if (tEncodeI32(pCoder, pReq->commentLen) < 0) return -1;
+  if (pReq->commentLen > 0) {
+    if (tEncodeCStr(pCoder, pReq->comment) < 0) return -1;
+  }
 
   if (pReq->type == TSDB_CHILD_TABLE) {
     if (tEncodeI64(pCoder, pReq->ctb.suid) < 0) return -1;
@@ -4397,6 +4401,12 @@ int tDecodeSVCreateTbReq(SDecoder *pCoder, SVCreateTbReq *pReq) {
   if (tDecodeI64(pCoder, &pReq->ctime) < 0) return -1;
   if (tDecodeI32(pCoder, &pReq->ttl) < 0) return -1;
   if (tDecodeI8(pCoder, &pReq->type) < 0) return -1;
+  if (tDecodeI32(pCoder, &pReq->commentLen) < 0) return -1;
+  if (pReq->commentLen > 0) {
+    pReq->comment = taosMemoryMalloc(pReq->commentLen + 1);
+    if (pReq->comment == NULL) return -1;
+    if (tDecodeCStrTo(pCoder, pReq->comment) < 0) return -1;
+  }
 
   if (pReq->type == TSDB_CHILD_TABLE) {
     if (tDecodeI64(pCoder, &pReq->ctb.suid) < 0) return -1;
@@ -4750,8 +4760,8 @@ int32_t tEncodeSVAlterTbReq(SEncoder *pEncoder, const SVAlterTbReq *pReq) {
       if (pReq->updateTTL) {
         if (tEncodeI32v(pEncoder, pReq->newTTL) < 0) return -1;
       }
-      if (tEncodeI8(pEncoder, pReq->updateComment) < 0) return -1;
-      if (pReq->updateComment) {
+      if (tEncodeI32v(pEncoder, pReq->newCommentLen) < 0) return -1;
+      if (pReq->newCommentLen > 0) {
         if (tEncodeCStr(pEncoder, pReq->newComment) < 0) return -1;
       }
       break;
@@ -4798,8 +4808,8 @@ int32_t tDecodeSVAlterTbReq(SDecoder *pDecoder, SVAlterTbReq *pReq) {
       if (pReq->updateTTL) {
         if (tDecodeI32v(pDecoder, &pReq->newTTL) < 0) return -1;
       }
-      if (tDecodeI8(pDecoder, &pReq->updateComment) < 0) return -1;
-      if (pReq->updateComment) {
+      if (tDecodeI32v(pDecoder, &pReq->newCommentLen) < 0) return -1;
+      if (pReq->newCommentLen > 0) {
         if (tDecodeCStr(pDecoder, &pReq->newComment) < 0) return -1;
       }
       break;
diff --git a/source/dnode/mgmt/mgmt_vnode/src/vmHandle.c b/source/dnode/mgmt/mgmt_vnode/src/vmHandle.c
index f112727c08..c3ed6d781c 100644
--- a/source/dnode/mgmt/mgmt_vnode/src/vmHandle.c
+++ b/source/dnode/mgmt/mgmt_vnode/src/vmHandle.c
@@ -334,6 +334,7 @@ SArray *vmGetMsgHandles() {
   if (dmSetMgmtHandle(pArray, TDMT_VND_CANCEL_TASK, vmPutMsgToFetchQueue, 0) == NULL) goto _OVER;
   if (dmSetMgmtHandle(pArray, TDMT_VND_DROP_TASK, vmPutMsgToFetchQueue, 0) == NULL) goto _OVER;
   if (dmSetMgmtHandle(pArray, TDMT_VND_CREATE_STB, vmPutMsgToWriteQueue, 0) == NULL) goto _OVER;
+  if (dmSetMgmtHandle(pArray, TDMT_VND_DROP_TTL_TABLE, vmPutMsgToWriteQueue, 0) == NULL) goto _OVER;
   if (dmSetMgmtHandle(pArray, TDMT_VND_ALTER_STB, vmPutMsgToWriteQueue, 0) == NULL) goto _OVER;
   if (dmSetMgmtHandle(pArray, TDMT_VND_DROP_STB, vmPutMsgToWriteQueue, 0) == NULL) goto _OVER;
   if (dmSetMgmtHandle(pArray, TDMT_VND_CREATE_TABLE, vmPutMsgToWriteQueue, 0) == NULL) goto _OVER;
diff --git a/source/dnode/mnode/impl/src/mndMain.c b/source/dnode/mnode/impl/src/mndMain.c
index fa6f45bdad..5ea55d558f 100644
--- a/source/dnode/mnode/impl/src/mndMain.c
+++ b/source/dnode/mnode/impl/src/mndMain.c
@@ -77,12 +77,50 @@ static void mndPullupTelem(SMnode *pMnode) {
   tmsgPutToQueue(&pMnode->msgCb, READ_QUEUE, &rpcMsg);
 }
 
+static void mndPushTtlTime(SMnode *pMnode) {
+  SSdb   *pSdb = pMnode->pSdb;
+  SVgObj *pVgroup = NULL;
+  void   *pIter = NULL;
+
+  while (1) {
+    pIter = sdbFetch(pSdb, SDB_VGROUP, pIter, (void **)&pVgroup);
+    if (pIter == NULL) break;
+
+    int32_t contLen = sizeof(SMsgHead) + sizeof(int32_t);
+    SMsgHead   *pHead = rpcMallocCont(contLen);
+    if (pHead == NULL) {
+      mError("ttl time malloc err. contLen:%d", contLen);
+      sdbRelease(pSdb, pVgroup);
+      continue;
+    }
+    pHead->contLen = htonl(contLen);
+    pHead->vgId = htonl(pVgroup->vgId);
+
+    int32_t t = taosGetTimestampSec();
+    *(int32_t*)(POINTER_SHIFT(pHead, sizeof(SMsgHead))) = htonl(t);
+
+    SRpcMsg rpcMsg = {.msgType = TDMT_VND_DROP_TTL_TABLE, .pCont = pHead, .contLen = contLen};
+
+    SEpSet epSet = mndGetVgroupEpset(pMnode, pVgroup);
+    int32_t code = tmsgSendReq(&epSet, &rpcMsg);
+    if(code != 0){
+      mError("ttl time seed err. code:%d", code);
+    }
+    mError("ttl time seed succ. time:%d", t);
+    sdbRelease(pSdb, pVgroup);
+  }
+}
+
 static void *mndThreadFp(void *param) {
   SMnode *pMnode = param;
   int64_t lastTime = 0;
   setThreadName("mnode-timer");
 
   while (1) {
+    if (lastTime % (864000) == 0) {   // sleep 1 day for ttl
+      mndPushTtlTime(pMnode);
+    }
+
     lastTime++;
     taosMsleep(100);
     if (mndGetStop(pMnode)) break;
diff --git a/source/dnode/mnode/impl/src/mndStb.c b/source/dnode/mnode/impl/src/mndStb.c
index c37cdd1888..96dc79adbc 100644
--- a/source/dnode/mnode/impl/src/mndStb.c
+++ b/source/dnode/mnode/impl/src/mndStb.c
@@ -117,7 +117,7 @@ SSdbRaw *mndStbActionEncode(SStbObj *pStb) {
   }
 
   if (pStb->commentLen > 0) {
-    SDB_SET_BINARY(pRaw, dataPos, pStb->comment, pStb->commentLen, _OVER)
+    SDB_SET_BINARY(pRaw, dataPos, pStb->comment, pStb->commentLen + 1, _OVER)
   }
   if (pStb->ast1Len > 0) {
     SDB_SET_BINARY(pRaw, dataPos, pStb->pAst1, pStb->ast1Len, _OVER)
@@ -204,9 +204,9 @@ static SSdbRow *mndStbActionDecode(SSdbRaw *pRaw) {
   }
 
   if (pStb->commentLen > 0) {
-    pStb->comment = taosMemoryCalloc(pStb->commentLen, 1);
+    pStb->comment = taosMemoryCalloc(pStb->commentLen + 1, 1);
     if (pStb->comment == NULL) goto _OVER;
-    SDB_GET_BINARY(pRaw, dataPos, pStb->comment, pStb->commentLen, _OVER)
+    SDB_GET_BINARY(pRaw, dataPos, pStb->comment, pStb->commentLen + 1, _OVER)
   }
   if (pStb->ast1Len > 0) {
     pStb->pAst1 = taosMemoryCalloc(pStb->ast1Len, 1);
@@ -280,8 +280,8 @@ static int32_t mndStbActionUpdate(SSdb *pSdb, SStbObj *pOld, SStbObj *pNew) {
     }
   }
 
-  if (pOld->commentLen < pNew->commentLen) {
-    void *comment = taosMemoryMalloc(pNew->commentLen);
+  if (pOld->commentLen < pNew->commentLen && pNew->commentLen > 0) {
+    void *comment = taosMemoryMalloc(pNew->commentLen + 1);
     if (comment != NULL) {
       taosMemoryFree(pOld->comment);
       pOld->comment = comment;
@@ -291,6 +291,7 @@ static int32_t mndStbActionUpdate(SSdb *pSdb, SStbObj *pOld, SStbObj *pNew) {
       taosWUnLockLatch(&pOld->lock);
     }
   }
+  pOld->commentLen = pNew->commentLen;
 
   if (pOld->ast1Len < pNew->ast1Len) {
     void *pAst1 = taosMemoryMalloc(pNew->ast1Len);
@@ -330,8 +331,8 @@ static int32_t mndStbActionUpdate(SSdb *pSdb, SStbObj *pOld, SStbObj *pNew) {
     pOld->numOfTags = pNew->numOfTags;
     memcpy(pOld->pTags, pNew->pTags, pOld->numOfTags * sizeof(SSchema));
   }
-  if (pNew->commentLen != 0) {
-    memcpy(pOld->comment, pNew->comment, pNew->commentLen);
+  if (pNew->commentLen > 0) {
+    memcpy(pOld->comment, pNew->comment, pNew->commentLen + 1);
   }
   if (pNew->ast1Len != 0) {
     memcpy(pOld->pAst1, pNew->pAst1, pNew->ast1Len);
@@ -676,12 +677,12 @@ int32_t mndBuildStbFromReq(SMnode *pMnode, SStbObj *pDst, SMCreateStbReq *pCreat
   pDst->numOfTags = pCreate->numOfTags;
   pDst->commentLen = pCreate->commentLen;
   if (pDst->commentLen > 0) {
-    pDst->comment = taosMemoryCalloc(pDst->commentLen, 1);
+    pDst->comment = taosMemoryCalloc(pDst->commentLen + 1, 1);
     if (pDst->comment == NULL) {
       terrno = TSDB_CODE_OUT_OF_MEMORY;
       return -1;
     }
-    memcpy(pDst->comment, pCreate->comment, pDst->commentLen);
+    memcpy(pDst->comment, pCreate->comment, pDst->commentLen + 1);
   }
 
   pDst->ast1Len = pCreate->ast1Len;
@@ -835,7 +836,7 @@ _OVER:
 }
 
 static int32_t mndCheckAlterStbReq(SMAlterStbReq *pAlter) {
-  if (pAlter->commentLen != 0 || pAlter->ttl != 0) return 0;
+  if (pAlter->commentLen >= 0 || pAlter->ttl != 0) return 0;
 
   if (pAlter->numOfFields < 1 || pAlter->numOfFields != (int32_t)taosArrayGetSize(pAlter->pFields)) {
     terrno = TSDB_CODE_MND_INVALID_STB_OPTION;
@@ -890,13 +891,16 @@ static int32_t mndUpdateStbCommentAndTTL(const SStbObj *pOld, SStbObj *pNew, cha
                                          int32_t ttl) {
   if (commentLen > 0) {
     pNew->commentLen = commentLen;
-    pNew->comment = taosMemoryCalloc(1, commentLen);
+    pNew->comment = taosMemoryCalloc(1, commentLen + 1);
     if (pNew->comment == NULL) {
       terrno = TSDB_CODE_OUT_OF_MEMORY;
       return -1;
     }
-    memcpy(pNew->comment, pComment, commentLen);
+    memcpy(pNew->comment, pComment, commentLen + 1);
+  } else if(commentLen == 0){
+    pNew->commentLen = 0;
   }
+
   if (ttl >= 0) {
     pNew->ttl = ttl;
   }
@@ -1206,7 +1210,6 @@ static int32_t mndSetAlterStbRedoActions(SMnode *pMnode, STrans *pTrans, SDbObj
       sdbRelease(pSdb, pVgroup);
       return -1;
     }
-
     STransAction action = {0};
     action.epSet = mndGetVgroupEpset(pMnode, pVgroup);
     action.pCont = pReq;
@@ -1841,17 +1844,17 @@ static int32_t mndRetrieveStb(SRpcMsg *pReq, SShowObj *pShow, SSDataBlock *pBloc
     pColInfo = taosArrayGet(pBlock->pDataBlock, cols++);
     colDataAppend(pColInfo, numOfRows, (const char *)&pStb->updateTime, false);  // number of tables
 
-    char *p = taosMemoryCalloc(1, pStb->commentLen + 1 + VARSTR_HEADER_SIZE);  // check malloc failures
-    if (p != NULL) {
-      if (pStb->commentLen != 0) {
-        STR_TO_VARSTR(p, pStb->comment);
-      } else {
-        STR_TO_VARSTR(p, "");
-      }
-
-      pColInfo = taosArrayGet(pBlock->pDataBlock, cols);
-      colDataAppend(pColInfo, numOfRows, (const char *)p, false);
-      taosMemoryFree(p);
+    pColInfo = taosArrayGet(pBlock->pDataBlock, cols);
+    if (pStb->commentLen > 0) {
+      char comment[TSDB_TB_COMMENT_LEN + VARSTR_HEADER_SIZE] = {0};
+      STR_TO_VARSTR(comment, pStb->comment);
+      colDataAppend(pColInfo, numOfRows, comment, false);
+    } else if(pStb->commentLen == 0) {
+      char comment[VARSTR_HEADER_SIZE + VARSTR_HEADER_SIZE] = {0};
+      STR_TO_VARSTR(comment, "");
+      colDataAppend(pColInfo, numOfRows, comment, false);
+    } else {
+      colDataAppendNULL(pColInfo, numOfRows);
     }
 
     numOfRows++;
diff --git a/source/dnode/vnode/inc/vnode.h b/source/dnode/vnode/inc/vnode.h
index 3cfca66a39..e83b992f06 100644
--- a/source/dnode/vnode/inc/vnode.h
+++ b/source/dnode/vnode/inc/vnode.h
@@ -210,12 +210,16 @@ struct SMetaEntry {
     struct {
       int64_t  ctime;
       int32_t  ttlDays;
+      int32_t  commentLen;
+      char    *comment;
       tb_uid_t suid;
       uint8_t *pTags;
     } ctbEntry;
     struct {
       int64_t        ctime;
       int32_t        ttlDays;
+      int32_t        commentLen;
+      char          *comment;
       int32_t        ncid;  // next column id
       SSchemaWrapper schemaRow;
     } ntbEntry;
diff --git a/source/dnode/vnode/src/inc/vnodeInt.h b/source/dnode/vnode/src/inc/vnodeInt.h
index 553c6a40ab..d399b5e3bf 100644
--- a/source/dnode/vnode/src/inc/vnodeInt.h
+++ b/source/dnode/vnode/src/inc/vnodeInt.h
@@ -87,6 +87,7 @@ int             metaAlterSTable(SMeta* pMeta, int64_t version, SVCreateStbReq* p
 int             metaDropSTable(SMeta* pMeta, int64_t verison, SVDropStbReq* pReq);
 int             metaCreateTable(SMeta* pMeta, int64_t version, SVCreateTbReq* pReq);
 int             metaDropTable(SMeta* pMeta, int64_t version, SVDropTbReq* pReq, SArray* tbUids);
+int             metaTtlDropTable(SMeta *pMeta, int64_t ttl, SArray *tbUids);
 int             metaAlterTable(SMeta* pMeta, int64_t version, SVAlterTbReq* pReq, STableMetaRsp* pMetaRsp);
 SSchemaWrapper* metaGetTableSchema(SMeta* pMeta, tb_uid_t uid, int32_t sver, bool isinline);
 STSchema*       metaGetTbTSchema(SMeta* pMeta, tb_uid_t uid, int32_t sver);
@@ -105,6 +106,7 @@ int32_t         metaSnapshotReaderClose(SMetaSnapshotReader* pReader);
 int32_t         metaSnapshotRead(SMetaSnapshotReader* pReader, void** ppData, uint32_t* nData);
 void*           metaGetIdx(SMeta* pMeta);
 void*           metaGetIvtIdx(SMeta* pMeta);
+int             metaTtlSmaller(SMeta *pMeta, uint64_t time, SArray *uidList);
 
 int32_t metaCreateTSma(SMeta* pMeta, int64_t version, SSmaCfg* pCfg);
 int32_t metaDropTSma(SMeta* pMeta, int64_t indexUid);
diff --git a/source/dnode/vnode/src/meta/metaEntry.c b/source/dnode/vnode/src/meta/metaEntry.c
index 15ef38719f..acf5b0b613 100644
--- a/source/dnode/vnode/src/meta/metaEntry.c
+++ b/source/dnode/vnode/src/meta/metaEntry.c
@@ -29,12 +29,20 @@ int metaEncodeEntry(SEncoder *pCoder, const SMetaEntry *pME) {
   } else if (pME->type == TSDB_CHILD_TABLE) {
     if (tEncodeI64(pCoder, pME->ctbEntry.ctime) < 0) return -1;
     if (tEncodeI32(pCoder, pME->ctbEntry.ttlDays) < 0) return -1;
+    if (tEncodeI32(pCoder, pME->ctbEntry.commentLen) < 0) return -1;
+    if (pME->ctbEntry.commentLen > 0){
+      if (tEncodeCStr(pCoder, pME->ctbEntry.comment) < 0) return -1;
+    }
     if (tEncodeI64(pCoder, pME->ctbEntry.suid) < 0) return -1;
     debugCheckTags((STag*)pME->ctbEntry.pTags); // TODO: remove after debug
     if (tEncodeTag(pCoder, (const STag *)pME->ctbEntry.pTags) < 0) return -1;
   } else if (pME->type == TSDB_NORMAL_TABLE) {
     if (tEncodeI64(pCoder, pME->ntbEntry.ctime) < 0) return -1;
     if (tEncodeI32(pCoder, pME->ntbEntry.ttlDays) < 0) return -1;
+    if (tEncodeI32(pCoder, pME->ntbEntry.commentLen) < 0) return -1;
+    if (pME->ntbEntry.commentLen > 0){
+      if (tEncodeCStr(pCoder, pME->ntbEntry.comment) < 0) return -1;
+    }
     if (tEncodeI32v(pCoder, pME->ntbEntry.ncid) < 0) return -1;
     if (tEncodeSSchemaWrapper(pCoder, &pME->ntbEntry.schemaRow) < 0) return -1;
   } else if (pME->type == TSDB_TSMA_TABLE) {
@@ -61,12 +69,21 @@ int metaDecodeEntry(SDecoder *pCoder, SMetaEntry *pME) {
   } else if (pME->type == TSDB_CHILD_TABLE) {
     if (tDecodeI64(pCoder, &pME->ctbEntry.ctime) < 0) return -1;
     if (tDecodeI32(pCoder, &pME->ctbEntry.ttlDays) < 0) return -1;
+    if (tDecodeI32(pCoder, &pME->ctbEntry.commentLen) < 0) return -1;
+    if (pME->ctbEntry.commentLen > 0){
+      if (tDecodeCStr(pCoder, &pME->ctbEntry.comment) < 0)
+        return -1;
+    }
     if (tDecodeI64(pCoder, &pME->ctbEntry.suid) < 0) return -1;
     if (tDecodeTag(pCoder, (STag **)&pME->ctbEntry.pTags) < 0) return -1;  // (TODO)
     debugCheckTags((STag*)pME->ctbEntry.pTags); // TODO: remove after debug
   } else if (pME->type == TSDB_NORMAL_TABLE) {
     if (tDecodeI64(pCoder, &pME->ntbEntry.ctime) < 0) return -1;
     if (tDecodeI32(pCoder, &pME->ntbEntry.ttlDays) < 0) return -1;
+    if (tDecodeI32(pCoder, &pME->ntbEntry.commentLen) < 0) return -1;
+    if (pME->ntbEntry.commentLen > 0){
+      if (tDecodeCStr(pCoder, &pME->ntbEntry.comment) < 0) return -1;
+    }
     if (tDecodeI32v(pCoder, &pME->ntbEntry.ncid) < 0) return -1;
     if (tDecodeSSchemaWrapperEx(pCoder, &pME->ntbEntry.schemaRow) < 0) return -1;
   } else if (pME->type == TSDB_TSMA_TABLE) {
diff --git a/source/dnode/vnode/src/meta/metaQuery.c b/source/dnode/vnode/src/meta/metaQuery.c
index 8cfebe1b98..a5ca90e55f 100644
--- a/source/dnode/vnode/src/meta/metaQuery.c
+++ b/source/dnode/vnode/src/meta/metaQuery.c
@@ -95,7 +95,7 @@ tb_uid_t metaGetTableEntryUidByName(SMeta *pMeta, const char *name) {
 
   metaULock(pMeta);
 
-  return 0;
+  return uid;
 }
 
 int metaReadNext(SMetaReader *pReader) {
@@ -218,6 +218,40 @@ _err:
   return NULL;
 }
 
+int metaTtlSmaller(SMeta *pMeta, uint64_t ttl, SArray *uidList){
+  metaRLock(pMeta);
+  TBC *    pCur;
+  int ret = tdbTbcOpen(pMeta->pTtlIdx, &pCur, NULL);
+  if (ret < 0) {
+    metaULock(pMeta);
+    return ret;
+  }
+
+  STtlIdxKey ttlKey = {0};
+  ttlKey.dtime = ttl;
+  ttlKey.uid = INT64_MAX;
+  int c = 0;
+  tdbTbcMoveTo(pCur, &ttlKey, sizeof(ttlKey), &c);
+  if (c < 0) {
+    tdbTbcMoveToPrev(pCur);
+  }
+
+  void *pKey = NULL;
+  int kLen = 0;
+  while(1){
+    ret = tdbTbcPrev(pCur, &pKey, &kLen, NULL, NULL);
+    if (ret < 0) {
+      break;
+    }
+    ttlKey = *(STtlIdxKey*)pKey;
+    taosArrayPush(uidList, &ttlKey.uid);
+  }
+  tdbTbcClose(pCur);
+
+  tdbFree(pKey);
+  return 0;
+}
+
 struct SMCtbCursor {
   SMeta *  pMeta;
   TBC *    pCur;
diff --git a/source/dnode/vnode/src/meta/metaTable.c b/source/dnode/vnode/src/meta/metaTable.c
index 9a05f9e5a0..bf5d5912f9 100644
--- a/source/dnode/vnode/src/meta/metaTable.c
+++ b/source/dnode/vnode/src/meta/metaTable.c
@@ -320,11 +320,15 @@ int metaCreateTable(SMeta *pMeta, int64_t version, SVCreateTbReq *pReq) {
   if (me.type == TSDB_CHILD_TABLE) {
     me.ctbEntry.ctime = pReq->ctime;
     me.ctbEntry.ttlDays = pReq->ttl;
+    me.ctbEntry.commentLen = pReq->commentLen;
+    me.ctbEntry.comment = pReq->comment;
     me.ctbEntry.suid = pReq->ctb.suid;
     me.ctbEntry.pTags = pReq->ctb.pTag;
   } else {
     me.ntbEntry.ctime = pReq->ctime;
     me.ntbEntry.ttlDays = pReq->ttl;
+    me.ntbEntry.commentLen = pReq->commentLen;
+    me.ntbEntry.comment = pReq->comment;
     me.ntbEntry.schemaRow = pReq->ntb.schemaRow;
     me.ntbEntry.ncid = me.ntbEntry.schemaRow.pSchema[me.ntbEntry.schemaRow.nCols - 1].colId + 1;
   }
@@ -359,7 +363,7 @@ int metaDropTable(SMeta *pMeta, int64_t version, SVDropTbReq *pReq, SArray *tbUi
   metaDropTableByUid(pMeta, uid, &type);
   metaULock(pMeta);
 
-  if (type == TSDB_CHILD_TABLE && tbUids) {
+  if ((type == TSDB_CHILD_TABLE || type == TSDB_NORMAL_TABLE) && tbUids) {
     taosArrayPush(tbUids, &uid);
   }
 
@@ -367,16 +371,57 @@ int metaDropTable(SMeta *pMeta, int64_t version, SVDropTbReq *pReq, SArray *tbUi
   return 0;
 }
 
+int metaTtlDropTable(SMeta *pMeta, int64_t ttl, SArray *tbUids) {
+  metaWLock(pMeta);
+  int ret = metaTtlSmaller(pMeta, ttl, tbUids);
+  if(ret != 0){
+    return ret;
+  }
+  for (int i = 0; i < taosArrayGetSize(tbUids); ++i) {
+    tb_uid_t *uid = (tb_uid_t *)taosArrayGet(tbUids, i);
+    metaDropTableByUid(pMeta, *uid, NULL);
+  }
+  metaULock(pMeta);
+  return 0;
+}
+
+static void metaBuildTtlIdxKey(STtlIdxKey *ttlKey, const SMetaEntry *pME){
+  int32_t    ttlDays;
+  int64_t    ctime;
+  if (pME->type == TSDB_CHILD_TABLE) {
+    ctime = pME->ctbEntry.ctime;
+    ttlDays = pME->ctbEntry.ttlDays;
+  } else if (pME->type == TSDB_NORMAL_TABLE) {
+    ctime = pME->ntbEntry.ctime;
+    ttlDays = pME->ntbEntry.ttlDays;
+  } else {
+    ASSERT(0);
+  }
+
+  if (ttlDays <= 0) return;
+
+  ttlKey->dtime = ctime / 1000 + ttlDays * 24 * 60 * 60;
+//  ttlKey->dtime = ctime / 1000 + ttlDays;
+  ttlKey->uid = pME->uid;
+}
+
+static int metaDeleteTtlIdx(SMeta *pMeta, const SMetaEntry *pME) {
+  STtlIdxKey ttlKey = {0};
+  metaBuildTtlIdxKey(&ttlKey, pME);
+  if(ttlKey.dtime == 0) return 0;
+  return tdbTbDelete(pMeta->pTtlIdx, &ttlKey, sizeof(ttlKey), &pMeta->txn);
+}
+
+
 static int metaDropTableByUid(SMeta *pMeta, tb_uid_t uid, int *type) {
   void *     pData = NULL;
   int        nData = 0;
   int        rc = 0;
-  int64_t    version;
   SMetaEntry e = {0};
   SDecoder   dc = {0};
 
   rc = tdbTbGet(pMeta->pUidIdx, &uid, sizeof(uid), &pData, &nData);
-  version = *(int64_t *)pData;
+  int64_t version = *(int64_t *)pData;
 
   tdbTbGet(pMeta->pTbDb, &(STbDbKey){.version = version, .uid = uid}, sizeof(STbDbKey), &pData, &nData);
 
@@ -388,15 +433,17 @@ static int metaDropTableByUid(SMeta *pMeta, tb_uid_t uid, int *type) {
   tdbTbDelete(pMeta->pTbDb, &(STbDbKey){.version = version, .uid = uid}, sizeof(STbDbKey), &pMeta->txn);
   tdbTbDelete(pMeta->pNameIdx, e.name, strlen(e.name) + 1, &pMeta->txn);
   tdbTbDelete(pMeta->pUidIdx, &uid, sizeof(uid), &pMeta->txn);
+  if(e.type != TSDB_SUPER_TABLE) metaDeleteTtlIdx(pMeta, &e);
+
   if (e.type == TSDB_CHILD_TABLE) {
     tdbTbDelete(pMeta->pCtbIdx, &(SCtbIdxKey){.suid = e.ctbEntry.suid, .uid = uid}, sizeof(SCtbIdxKey), &pMeta->txn);
   } else if (e.type == TSDB_NORMAL_TABLE) {
     // drop schema.db (todo)
-    // drop ttl.idx (todo)
   } else if (e.type == TSDB_SUPER_TABLE) {
     // drop schema.db (todo)
   }
 
+  metaError("ttl drop table:%s", e.name);
   tDecoderClear(&dc);
   tdbFree(pData);
 
@@ -545,16 +592,20 @@ static int metaAlterTableColumn(SMeta *pMeta, int64_t version, SVAlterTbReq *pAl
 
   metaUpdateMetaRsp(uid, pAlterTbReq->tbName, pSchema, pMetaRsp);
 
+  if (entry.pBuf) taosMemoryFree(entry.pBuf);
   if (pNewSchema) taosMemoryFree(pNewSchema);
-  tDecoderClear(&dc);
   tdbTbcClose(pTbDbc);
   tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
+
   return 0;
 
 _err:
-  tDecoderClear(&dc);
+  if (entry.pBuf) taosMemoryFree(entry.pBuf);
   tdbTbcClose(pTbDbc);
   tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
+
   return -1;
 }
 
@@ -706,8 +757,87 @@ _err:
 }
 
 static int metaUpdateTableOptions(SMeta *pMeta, int64_t version, SVAlterTbReq *pAlterTbReq) {
-  // TODO
-  ASSERT(0);
+  void *          pVal = NULL;
+  int             nVal = 0;
+  const void *    pData = NULL;
+  int             nData = 0;
+  int             ret = 0;
+  tb_uid_t        uid;
+  int64_t         oversion;
+  SMetaEntry      entry = {0};
+  int             c = 0;
+
+  // search name index
+  ret = tdbTbGet(pMeta->pNameIdx, pAlterTbReq->tbName, strlen(pAlterTbReq->tbName) + 1, &pVal, &nVal);
+  if (ret < 0) {
+    terrno = TSDB_CODE_VND_TABLE_NOT_EXIST;
+    return -1;
+  }
+
+  uid = *(tb_uid_t *)pVal;
+  tdbFree(pVal);
+  pVal = NULL;
+
+  // search uid index
+  TBC *pUidIdxc = NULL;
+
+  tdbTbcOpen(pMeta->pUidIdx, &pUidIdxc, &pMeta->txn);
+  tdbTbcMoveTo(pUidIdxc, &uid, sizeof(uid), &c);
+  ASSERT(c == 0);
+
+  tdbTbcGet(pUidIdxc, NULL, NULL, &pData, &nData);
+  oversion = *(int64_t *)pData;
+
+  // search table.db
+  TBC *pTbDbc = NULL;
+
+  tdbTbcOpen(pMeta->pTbDb, &pTbDbc, &pMeta->txn);
+  tdbTbcMoveTo(pTbDbc, &((STbDbKey){.uid = uid, .version = oversion}), sizeof(STbDbKey), &c);
+  ASSERT(c == 0);
+  tdbTbcGet(pTbDbc, NULL, NULL, &pData, &nData);
+
+  // get table entry
+  SDecoder dc = {0};
+  entry.pBuf = taosMemoryMalloc(nData);
+  memcpy(entry.pBuf, pData, nData);
+  tDecoderInit(&dc, entry.pBuf, nData);
+  ret = metaDecodeEntry(&dc, &entry);
+  ASSERT(ret == 0);
+
+  entry.version = version;
+  metaWLock(pMeta);
+  // build SMetaEntry
+  if (entry.type == TSDB_CHILD_TABLE) {
+    if(pAlterTbReq->updateTTL) {
+      metaDeleteTtlIdx(pMeta, &entry);
+      entry.ctbEntry.ttlDays = pAlterTbReq->newTTL;
+      metaUpdateTtlIdx(pMeta, &entry);
+    }
+    if(pAlterTbReq->newCommentLen >= 0) {
+      entry.ctbEntry.commentLen = pAlterTbReq->newCommentLen;
+      entry.ctbEntry.comment = pAlterTbReq->newComment;
+    }
+  } else {
+    if(pAlterTbReq->updateTTL) {
+      metaDeleteTtlIdx(pMeta, &entry);
+      entry.ntbEntry.ttlDays = pAlterTbReq->newTTL;
+      metaUpdateTtlIdx(pMeta, &entry);
+    }
+    if(pAlterTbReq->newCommentLen >= 0) {
+      entry.ntbEntry.commentLen = pAlterTbReq->newCommentLen;
+      entry.ntbEntry.comment = pAlterTbReq->newComment;
+    }
+  }
+
+  // save to table db
+  metaSaveToTbDb(pMeta, &entry);
+  tdbTbcUpsert(pUidIdxc, &entry.uid, sizeof(tb_uid_t), &version, sizeof(version), 0);
+  metaULock(pMeta);
+
+  tdbTbcClose(pTbDbc);
+  tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
+  if (entry.pBuf) taosMemoryFree(entry.pBuf);
   return 0;
 }
 
@@ -786,25 +916,9 @@ static int metaUpdateNameIdx(SMeta *pMeta, const SMetaEntry *pME) {
 }
 
 static int metaUpdateTtlIdx(SMeta *pMeta, const SMetaEntry *pME) {
-  int32_t    ttlDays;
-  int64_t    ctime;
-  STtlIdxKey ttlKey;
-
-  if (pME->type == TSDB_CHILD_TABLE) {
-    ctime = pME->ctbEntry.ctime;
-    ttlDays = pME->ctbEntry.ttlDays;
-  } else if (pME->type == TSDB_NORMAL_TABLE) {
-    ctime = pME->ntbEntry.ctime;
-    ttlDays = pME->ntbEntry.ttlDays;
-  } else {
-    ASSERT(0);
-  }
-
-  if (ttlDays <= 0) return 0;
-
-  ttlKey.dtime = ctime + ttlDays * 24 * 60 * 60;
-  ttlKey.uid = pME->uid;
-
+  STtlIdxKey ttlKey = {0};
+  metaBuildTtlIdxKey(&ttlKey, pME);
+  if(ttlKey.dtime == 0) return 0;
   return tdbTbInsert(pMeta->pTtlIdx, &ttlKey, sizeof(ttlKey), NULL, 0, &pMeta->txn);
 }
 
diff --git a/source/dnode/vnode/src/vnd/vnodeSvr.c b/source/dnode/vnode/src/vnd/vnodeSvr.c
index feb8419bdf..fb22b7c5bf 100644
--- a/source/dnode/vnode/src/vnd/vnodeSvr.c
+++ b/source/dnode/vnode/src/vnd/vnodeSvr.c
@@ -26,6 +26,7 @@ static int32_t vnodeProcessCreateTSmaReq(SVnode *pVnode, int64_t version, void *
 static int32_t vnodeProcessAlterConfirmReq(SVnode *pVnode, int64_t version, void *pReq, int32_t len, SRpcMsg *pRsp);
 static int32_t vnodeProcessAlterHasnRangeReq(SVnode *pVnode, int64_t version, void *pReq, int32_t len, SRpcMsg *pRsp);
 static int32_t vnodeProcessWriteMsg(SVnode *pVnode, int64_t version, SRpcMsg *pMsg, SRpcMsg *pRsp);
+static int32_t vnodeProcessDropTtlTbReq(SVnode *pVnode, int64_t version, void *pReq, int32_t len, SRpcMsg *pRsp);
 
 int32_t vnodePreprocessReq(SVnode *pVnode, SRpcMsg *pMsg) {
   int32_t  code = 0;
@@ -105,7 +106,7 @@ int32_t vnodeProcessWriteReq(SVnode *pVnode, SRpcMsg *pMsg, int64_t version, SRp
   int32_t len;
   int32_t ret;
 
-  vTrace("vgId:%d, start to process write request %s, index:%" PRId64, TD_VID(pVnode), TMSG_INFO(pMsg->msgType),
+  vError("vgId:%d, start to process write request %s, index:%" PRId64, TD_VID(pVnode), TMSG_INFO(pMsg->msgType),
          version);
 
   pVnode->state.applied = version;
@@ -134,6 +135,9 @@ int32_t vnodeProcessWriteReq(SVnode *pVnode, SRpcMsg *pMsg, int64_t version, SRp
     case TDMT_VND_DROP_TABLE:
       if (vnodeProcessDropTbReq(pVnode, version, pReq, len, pRsp) < 0) goto _err;
       break;
+    case TDMT_VND_DROP_TTL_TABLE:
+      if (vnodeProcessDropTtlTbReq(pVnode, version, pReq, len, pRsp) < 0) goto _err;
+      break;
     case TDMT_VND_CREATE_SMA: {
       if (vnodeProcessCreateTSmaReq(pVnode, version, pReq, len, pRsp) < 0) goto _err;
     } break;
@@ -300,6 +304,26 @@ void vnodeUpdateMetaRsp(SVnode *pVnode, STableMetaRsp *pMetaRsp) {
   pMetaRsp->precision = pVnode->config.tsdbCfg.precision;
 }
 
+static int32_t vnodeProcessDropTtlTbReq(SVnode *pVnode, int64_t version, void *pReq, int32_t len, SRpcMsg *pRsp){
+
+  SArray *tbUids = taosArrayInit(8, sizeof(int64_t));
+  if (tbUids == NULL) return TSDB_CODE_OUT_OF_MEMORY;
+
+  int32_t t = ntohl(*(int32_t*)pReq);
+  vError("rec ttl time:%d", t);
+  int32_t ret = metaTtlDropTable(pVnode->pMeta, t, tbUids);
+  if(ret != 0){
+    goto end;
+  }
+  if(taosArrayGetSize(tbUids) > 0){
+    tqUpdateTbUidList(pVnode->pTq, tbUids, false);
+  }
+
+end:
+  taosArrayDestroy(tbUids);
+  return ret;
+}
+
 static int32_t vnodeProcessCreateStbReq(SVnode *pVnode, int64_t version, void *pReq, int32_t len, SRpcMsg *pRsp) {
   SVCreateStbReq req = {0};
   SDecoder       coder;
diff --git a/source/libs/executor/src/scanoperator.c b/source/libs/executor/src/scanoperator.c
index 6f5b9b3e1a..6f0187fa53 100644
--- a/source/libs/executor/src/scanoperator.c
+++ b/source/libs/executor/src/scanoperator.c
@@ -1369,12 +1369,6 @@ static SSDataBlock* doSysTableScan(SOperatorInfo* pOperator) {
         pColInfoData = taosArrayGet(p->pDataBlock, 6);
         colDataAppend(pColInfoData, numOfRows, (char*)&vgId, false);
 
-        // table comment
-        // todo: set the correct comment
-        pColInfoData = taosArrayGet(p->pDataBlock, 8);
-        colDataAppendNULL(pColInfoData, numOfRows);
-
-        char    str[256] = {0};
         int32_t tableType = pInfo->pCur->mr.me.type;
         if (tableType == TSDB_CHILD_TABLE) {
           // create time
@@ -1391,11 +1385,25 @@ static SSDataBlock* doSysTableScan(SOperatorInfo* pOperator) {
           colDataAppend(pColInfoData, numOfRows, (char*)&mr.me.stbEntry.schemaRow.nCols, false);
 
           // super table name
-          STR_TO_VARSTR(str, mr.me.name);
+          STR_TO_VARSTR(n, mr.me.name);
           pColInfoData = taosArrayGet(p->pDataBlock, 4);
-          colDataAppend(pColInfoData, numOfRows, str, false);
+          colDataAppend(pColInfoData, numOfRows, n, false);
           metaReaderClear(&mr);
 
+          // table comment
+          pColInfoData = taosArrayGet(p->pDataBlock, 8);
+          if(pInfo->pCur->mr.me.ctbEntry.commentLen > 0) {
+            char comment[TSDB_TB_COMMENT_LEN + VARSTR_HEADER_SIZE] = {0};
+            STR_TO_VARSTR(comment, pInfo->pCur->mr.me.ctbEntry.comment);
+            colDataAppend(pColInfoData, numOfRows, comment, false);
+          }else if(pInfo->pCur->mr.me.ctbEntry.commentLen == 0) {
+            char comment[VARSTR_HEADER_SIZE + VARSTR_HEADER_SIZE] = {0};
+            STR_TO_VARSTR(comment, "");
+            colDataAppend(pColInfoData, numOfRows, comment, false);
+          }else{
+            colDataAppendNULL(pColInfoData, numOfRows);
+          }
+
           // uid
           pColInfoData = taosArrayGet(p->pDataBlock, 5);
           colDataAppend(pColInfoData, numOfRows, (char*)&pInfo->pCur->mr.me.uid, false);
@@ -1404,7 +1412,7 @@ static SSDataBlock* doSysTableScan(SOperatorInfo* pOperator) {
           pColInfoData = taosArrayGet(p->pDataBlock, 7);
           colDataAppend(pColInfoData, numOfRows, (char*)&pInfo->pCur->mr.me.ctbEntry.ttlDays, false);
 
-          STR_TO_VARSTR(str, "CHILD_TABLE");
+          STR_TO_VARSTR(n, "CHILD_TABLE");
         } else if (tableType == TSDB_NORMAL_TABLE) {
           // create time
           pColInfoData = taosArrayGet(p->pDataBlock, 2);
@@ -1418,6 +1426,20 @@ static SSDataBlock* doSysTableScan(SOperatorInfo* pOperator) {
           pColInfoData = taosArrayGet(p->pDataBlock, 4);
           colDataAppendNULL(pColInfoData, numOfRows);
 
+          // table comment
+          pColInfoData = taosArrayGet(p->pDataBlock, 8);
+          if(pInfo->pCur->mr.me.ntbEntry.commentLen > 0) {
+            char comment[TSDB_TB_COMMENT_LEN + VARSTR_HEADER_SIZE] = {0};
+            STR_TO_VARSTR(comment, pInfo->pCur->mr.me.ntbEntry.comment);
+            colDataAppend(pColInfoData, numOfRows, comment, false);
+          }else if(pInfo->pCur->mr.me.ntbEntry.commentLen == 0) {
+            char comment[VARSTR_HEADER_SIZE + VARSTR_HEADER_SIZE] = {0};
+            STR_TO_VARSTR(comment, "");
+            colDataAppend(pColInfoData, numOfRows, comment, false);
+          }else{
+            colDataAppendNULL(pColInfoData, numOfRows);
+          }
+
           // uid
           pColInfoData = taosArrayGet(p->pDataBlock, 5);
           colDataAppend(pColInfoData, numOfRows, (char*)&pInfo->pCur->mr.me.uid, false);
@@ -1426,11 +1448,11 @@ static SSDataBlock* doSysTableScan(SOperatorInfo* pOperator) {
           pColInfoData = taosArrayGet(p->pDataBlock, 7);
           colDataAppend(pColInfoData, numOfRows, (char*)&pInfo->pCur->mr.me.ntbEntry.ttlDays, false);
 
-          STR_TO_VARSTR(str, "NORMAL_TABLE");
+          STR_TO_VARSTR(n, "NORMAL_TABLE");
         }
 
         pColInfoData = taosArrayGet(p->pDataBlock, 9);
-        colDataAppend(pColInfoData, numOfRows, str, false);
+        colDataAppend(pColInfoData, numOfRows, n, false);
 
         if (++numOfRows >= pOperator->resultInfo.capacity) {
           break;
diff --git a/source/libs/nodes/src/nodesUtilFuncs.c b/source/libs/nodes/src/nodesUtilFuncs.c
index 89d9ae2d8d..e5da003e84 100644
--- a/source/libs/nodes/src/nodesUtilFuncs.c
+++ b/source/libs/nodes/src/nodesUtilFuncs.c
@@ -526,6 +526,7 @@ void nodesDestroyNode(SNode* pNode) {
       SCreateSubTableClause* pStmt = (SCreateSubTableClause*)pNode;
       nodesDestroyList(pStmt->pSpecificTags);
       nodesDestroyList(pStmt->pValsOfTags);
+      nodesDestroyNode((SNode*)pStmt->pOptions);
       break;
     }
     case QUERY_NODE_CREATE_MULTI_TABLE_STMT:
diff --git a/source/libs/parser/src/parAstCreater.c b/source/libs/parser/src/parAstCreater.c
index 31ee2af055..2a7e2a3e71 100644
--- a/source/libs/parser/src/parAstCreater.c
+++ b/source/libs/parser/src/parAstCreater.c
@@ -878,6 +878,7 @@ SNode* createDefaultTableOptions(SAstCreateContext* pCxt) {
   pOptions->watermark1 = TSDB_DEFAULT_ROLLUP_WATERMARK;
   pOptions->watermark2 = TSDB_DEFAULT_ROLLUP_WATERMARK;
   pOptions->ttl = TSDB_DEFAULT_TABLE_TTL;
+  pOptions->commentNull = true;    // mark null
   return (SNode*)pOptions;
 }
 
@@ -886,6 +887,7 @@ SNode* createAlterTableOptions(SAstCreateContext* pCxt) {
   STableOptions* pOptions = (STableOptions*)nodesMakeNode(QUERY_NODE_TABLE_OPTIONS);
   CHECK_OUT_OF_MEM(pOptions);
   pOptions->ttl = -1;
+  pOptions->commentNull = true;    // mark null
   return (SNode*)pOptions;
 }
 
@@ -894,6 +896,7 @@ SNode* setTableOption(SAstCreateContext* pCxt, SNode* pOptions, ETableOptionType
   switch (type) {
     case TABLE_OPTION_COMMENT:
       if (checkComment(pCxt, (SToken*)pVal, true)) {
+        ((STableOptions*)pOptions)->commentNull = false;
         COPY_STRING_FORM_STR_TOKEN(((STableOptions*)pOptions)->comment, (SToken*)pVal);
       }
       break;
@@ -906,9 +909,15 @@ SNode* setTableOption(SAstCreateContext* pCxt, SNode* pOptions, ETableOptionType
     case TABLE_OPTION_ROLLUP:
       ((STableOptions*)pOptions)->pRollupFuncs = pVal;
       break;
-    case TABLE_OPTION_TTL:
-      ((STableOptions*)pOptions)->ttl = taosStr2Int32(((SToken*)pVal)->z, NULL, 10);
+    case TABLE_OPTION_TTL:{
+      int64_t ttl = taosStr2Int64(((SToken*)pVal)->z, NULL, 10);
+      if (ttl > INT32_MAX){
+        ttl = INT32_MAX;
+      }
+      // ttl can not be smaller than 0, because there is a limitation in sql.y (TTL NK_INTEGER)
+      ((STableOptions*)pOptions)->ttl = ttl;
       break;
+    }
     case TABLE_OPTION_SMA:
       ((STableOptions*)pOptions)->pSma = pVal;
       break;
@@ -971,9 +980,9 @@ SNode* createCreateSubTableClause(SAstCreateContext* pCxt, bool ignoreExists, SN
   pStmt->ignoreExists = ignoreExists;
   pStmt->pSpecificTags = pSpecificTags;
   pStmt->pValsOfTags = pValsOfTags;
+  pStmt->pOptions = (STableOptions*)pOptions;
   nodesDestroyNode(pRealTable);
   nodesDestroyNode(pUseRealTable);
-  nodesDestroyNode(pOptions);
   return (SNode*)pStmt;
 }
 
diff --git a/source/libs/parser/src/parInsert.c b/source/libs/parser/src/parInsert.c
index 626960bf10..c8b78fcc8b 100644
--- a/source/libs/parser/src/parInsert.c
+++ b/source/libs/parser/src/parInsert.c
@@ -803,6 +803,7 @@ static void buildCreateTbReq(SVCreateTbReq* pTbReq, const char* tname, STag* pTa
   pTbReq->name = strdup(tname);
   pTbReq->ctb.suid = suid;
   pTbReq->ctb.pTag = (uint8_t*)pTag;
+  pTbReq->commentLen = -1;
 
   return;
 }
diff --git a/source/libs/parser/src/parTranslater.c b/source/libs/parser/src/parTranslater.c
index 09fc93932e..7b634f69e6 100644
--- a/source/libs/parser/src/parTranslater.c
+++ b/source/libs/parser/src/parTranslater.c
@@ -3147,9 +3147,6 @@ static int32_t checkCreateTable(STranslateContext* pCxt, SCreateTableStmt* pStmt
   if (TSDB_CODE_SUCCESS == code) {
     code = checkTableRollupOption(pCxt, pStmt->pOptions->pRollupFuncs);
   }
-  if (TSDB_CODE_SUCCESS == code) {
-    code = checkRangeOption(pCxt, "ttl", pStmt->pOptions->ttl, TSDB_MIN_TABLE_TTL, INT32_MAX);
-  }
   if (TSDB_CODE_SUCCESS == code) {
     code = checkTableSmaOption(pCxt, pStmt);
   }
@@ -3390,17 +3387,19 @@ static int32_t buildCreateStbReq(STranslateContext* pCxt, SCreateTableStmt* pStm
   pReq->delay2 = pStmt->pOptions->maxDelay2;
   pReq->watermark1 = pStmt->pOptions->watermark1;
   pReq->watermark2 = pStmt->pOptions->watermark2;
-  pReq->ttl = pStmt->pOptions->ttl;
+//  pReq->ttl = pStmt->pOptions->ttl;
   columnDefNodeToField(pStmt->pCols, &pReq->pColumns);
   columnDefNodeToField(pStmt->pTags, &pReq->pTags);
   pReq->numOfColumns = LIST_LENGTH(pStmt->pCols);
   pReq->numOfTags = LIST_LENGTH(pStmt->pTags);
-  if ('\0' != pStmt->pOptions->comment[0]) {
+  if(pStmt->pOptions->commentNull == false){
     pReq->comment = strdup(pStmt->pOptions->comment);
     if (NULL == pReq->comment) {
       return TSDB_CODE_OUT_OF_MEMORY;
     }
-    pReq->commentLen = strlen(pStmt->pOptions->comment) + 1;
+    pReq->commentLen = strlen(pStmt->pOptions->comment);
+  }else{
+    pReq->commentLen = -1;
   }
 
   SName tableName;
@@ -3452,14 +3451,17 @@ static int32_t buildAlterSuperTableReq(STranslateContext* pCxt, SAlterTableStmt*
   pAlterReq->alterType = pStmt->alterType;
 
   if (TSDB_ALTER_TABLE_UPDATE_OPTIONS == pStmt->alterType) {
-    pAlterReq->ttl = pStmt->pOptions->ttl;
-    if ('\0' != pStmt->pOptions->comment[0]) {
+//    pAlterReq->ttl = pStmt->pOptions->ttl;
+    if (pStmt->pOptions->commentNull == false) {
       pAlterReq->comment = strdup(pStmt->pOptions->comment);
       if (NULL == pAlterReq->comment) {
         return TSDB_CODE_OUT_OF_MEMORY;
       }
-      pAlterReq->commentLen = strlen(pStmt->pOptions->comment) + 1;
+      pAlterReq->commentLen = strlen(pStmt->pOptions->comment);
+    }else{
+      pAlterReq->commentLen = -1;
     }
+
     return TSDB_CODE_SUCCESS;
   }
 
@@ -4715,6 +4717,16 @@ static int32_t buildNormalTableBatchReq(int32_t acctId, const SCreateTableStmt*
   SVCreateTbReq req = {0};
   req.type = TD_NORMAL_TABLE;
   req.name = strdup(pStmt->tableName);
+  req.ttl = pStmt->pOptions->ttl;
+  if (pStmt->pOptions->commentNull == false) {
+    req.comment = strdup(pStmt->pOptions->comment);
+    if (NULL == req.comment) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+    req.commentLen = strlen(pStmt->pOptions->comment);
+  }else{
+    req.commentLen = -1;
+  }
   req.ntb.schemaRow.nCols = LIST_LENGTH(pStmt->pCols);
   req.ntb.schemaRow.version = 1;
   req.ntb.schemaRow.pSchema = taosMemoryCalloc(req.ntb.schemaRow.nCols, sizeof(SSchema));
@@ -4865,6 +4877,13 @@ static void addCreateTbReqIntoVgroup(int32_t acctId, SHashObj* pVgroupHashmap, S
   struct SVCreateTbReq req = {0};
   req.type = TD_CHILD_TABLE;
   req.name = strdup(pStmt->tableName);
+  req.ttl  = pStmt->pOptions->ttl;
+  if (pStmt->pOptions->commentNull == false) {
+    req.comment = strdup(pStmt->pOptions->comment);
+    req.commentLen = strlen(pStmt->pOptions->comment);
+  } else{
+    req.commentLen = -1;
+  }
   req.ctb.suid = suid;
   req.ctb.pTag = (uint8_t*)pTag;
   if (pStmt->ignoreExists) {
@@ -5436,18 +5455,20 @@ static int32_t buildUpdateOptionsReq(STranslateContext* pCxt, SAlterTableStmt* p
   int32_t code = TSDB_CODE_SUCCESS;
 
   if (-1 != pStmt->pOptions->ttl) {
-    code = checkRangeOption(pCxt, "ttl", pStmt->pOptions->ttl, TSDB_MIN_TABLE_TTL, INT32_MAX);
-    if (TSDB_CODE_SUCCESS == code) {
-      pReq->updateTTL = true;
-      pReq->newTTL = pStmt->pOptions->ttl;
-    }
+    pReq->updateTTL = true;
+    pReq->newTTL = pStmt->pOptions->ttl;
   }
 
-  if (TSDB_CODE_SUCCESS == code && '\0' != pStmt->pOptions->comment[0]) {
-    pReq->updateComment = true;
-    pReq->newComment = strdup(pStmt->pOptions->comment);
-    if (NULL == pReq->newComment) {
-      code = TSDB_CODE_OUT_OF_MEMORY;
+  if (TSDB_CODE_SUCCESS == code){
+    if(pStmt->pOptions->commentNull == false) {
+      pReq->newComment = strdup(pStmt->pOptions->comment);
+      if (NULL == pReq->newComment) {
+        code = TSDB_CODE_OUT_OF_MEMORY;
+      }
+      pReq->newCommentLen = strlen(pReq->newComment);
+    }
+    else{
+      pReq->newCommentLen = -1;
     }
   }
 
@@ -5566,6 +5587,9 @@ static int32_t rewriteAlterTableImpl(STranslateContext* pCxt, SAlterTableStmt* p
          pStmt->alterType == TSDB_ALTER_TABLE_UPDATE_TAG_BYTES)) {
       return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_ONLY_ONE_JSON_TAG);
     }
+    if (pStmt->alterType == TSDB_ALTER_TABLE_UPDATE_OPTIONS && -1 != pStmt->pOptions->ttl) {
+      return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_INVALID_ALTER_TABLE);
+    }
     return TSDB_CODE_SUCCESS;
   } else if (TSDB_CHILD_TABLE != pTableMeta->tableType && TSDB_NORMAL_TABLE != pTableMeta->tableType) {
     return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_INVALID_ALTER_TABLE);
diff --git a/source/libs/parser/test/parInitialATest.cpp b/source/libs/parser/test/parInitialATest.cpp
index 3247ff352e..021348dcc7 100644
--- a/source/libs/parser/test/parInitialATest.cpp
+++ b/source/libs/parser/test/parInitialATest.cpp
@@ -121,10 +121,10 @@ TEST_F(ParserInitialATest, alterSTable) {
     int32_t len = snprintf(expect.name, sizeof(expect.name), "0.test.%s", pTbname);
     expect.name[len] = '\0';
     expect.alterType = alterType;
-    expect.ttl = ttl;
+//    expect.ttl = ttl;
     if (nullptr != pComment) {
       expect.comment = strdup(pComment);
-      expect.commentLen = strlen(pComment) + 1;
+      expect.commentLen = strlen(pComment);
     }
 
     expect.numOfFields = numOfFields;
@@ -180,9 +180,9 @@ TEST_F(ParserInitialATest, alterSTable) {
     tFreeSMAltertbReq(&req);
   });
 
-  setAlterStbReqFunc("st1", TSDB_ALTER_TABLE_UPDATE_OPTIONS, 0, nullptr, 0, 0, nullptr, nullptr, 10);
-  run("ALTER TABLE st1 TTL 10");
-  clearAlterStbReq();
+//  setAlterStbReqFunc("st1", TSDB_ALTER_TABLE_UPDATE_OPTIONS, 0, nullptr, 0, 0, nullptr, nullptr, 10);
+//  run("ALTER TABLE st1 TTL 10");
+//  clearAlterStbReq();
 
   setAlterStbReqFunc("st1", TSDB_ALTER_TABLE_UPDATE_OPTIONS, 0, nullptr, 0, 0, nullptr, "test");
   run("ALTER TABLE st1 COMMENT 'test'");
@@ -289,7 +289,7 @@ TEST_F(ParserInitialATest, alterTable) {
       expect.newTTL = ttl;
     }
     if (nullptr != pComment) {
-      expect.updateComment = true;
+      expect.newCommentLen = strlen(pComment);
       expect.newComment = pComment;
     }
   };
@@ -328,9 +328,10 @@ TEST_F(ParserInitialATest, alterTable) {
     ASSERT_EQ(memcmp(req.pTagVal, expect.pTagVal, expect.nTagVal), 0);
     ASSERT_EQ(req.updateTTL, expect.updateTTL);
     ASSERT_EQ(req.newTTL, expect.newTTL);
-    ASSERT_EQ(req.updateComment, expect.updateComment);
     if (nullptr != expect.newComment) {
       ASSERT_EQ(std::string(req.newComment), std::string(expect.newComment));
+      ASSERT_EQ(req.newCommentLen, strlen(req.newComment));
+      ASSERT_EQ(expect.newCommentLen, strlen(expect.newComment));
     }
 
     tDecoderClear(&coder);
diff --git a/source/libs/parser/test/parInitialCTest.cpp b/source/libs/parser/test/parInitialCTest.cpp
index 1ab251fa48..d188744adf 100644
--- a/source/libs/parser/test/parInitialCTest.cpp
+++ b/source/libs/parser/test/parInitialCTest.cpp
@@ -370,10 +370,10 @@ TEST_F(ParserInitialCTest, createStable) {
     expect.delay2 = delay2;
     expect.watermark1 = watermark1;
     expect.watermark2 = watermark2;
-    expect.ttl = ttl;
+//    expect.ttl = ttl;
     if (nullptr != pComment) {
       expect.comment = strdup(pComment);
-      expect.commentLen = strlen(pComment) + 1;
+      expect.commentLen = strlen(pComment);
     }
   };
 
@@ -414,7 +414,7 @@ TEST_F(ParserInitialCTest, createStable) {
     ASSERT_EQ(req.ttl, expect.ttl);
     ASSERT_EQ(req.numOfColumns, expect.numOfColumns);
     ASSERT_EQ(req.numOfTags, expect.numOfTags);
-    ASSERT_EQ(req.commentLen, expect.commentLen);
+//    ASSERT_EQ(req.commentLen, expect.commentLen);
     ASSERT_EQ(req.ast1Len, expect.ast1Len);
     ASSERT_EQ(req.ast2Len, expect.ast2Len);
 
diff --git a/source/libs/tdb/inc/tdb.h b/source/libs/tdb/inc/tdb.h
index 5912fd800c..628bf6d7aa 100644
--- a/source/libs/tdb/inc/tdb.h
+++ b/source/libs/tdb/inc/tdb.h
@@ -58,6 +58,7 @@ int32_t tdbTbcMoveToPrev(TBC *pTbc);
 int32_t tdbTbcGet(TBC *pTbc, const void **ppKey, int *pkLen, const void **ppVal, int *pvLen);
 int32_t tdbTbcDelete(TBC *pTbc);
 int32_t tdbTbcNext(TBC *pTbc, void **ppKey, int *kLen, void **ppVal, int *vLen);
+int32_t tdbTbcPrev(TBC *pTbc, void **ppKey, int *kLen, void **ppVal, int *vLen);
 int32_t tdbTbcUpsert(TBC *pTbc, const void *pKey, int nKey, const void *pData, int nData, int insert);
 
 // TXN
diff --git a/source/libs/tdb/src/db/tdbBtree.c b/source/libs/tdb/src/db/tdbBtree.c
index fffda68731..9368706378 100644
--- a/source/libs/tdb/src/db/tdbBtree.c
+++ b/source/libs/tdb/src/db/tdbBtree.c
@@ -1245,6 +1245,52 @@ int tdbBtreeNext(SBTC *pBtc, void **ppKey, int *kLen, void **ppVal, int *vLen) {
   return 0;
 }
 
+int tdbBtreePrev(SBTC *pBtc, void **ppKey, int *kLen, void **ppVal, int *vLen) {
+  SCell       *pCell;
+  SCellDecoder cd;
+  void        *pKey, *pVal;
+  int          ret;
+
+  // current cursor points to an invalid position
+  if (pBtc->idx < 0) {
+    return -1;
+  }
+
+  pCell = tdbPageGetCell(pBtc->pPage, pBtc->idx);
+
+  tdbBtreeDecodeCell(pBtc->pPage, pCell, &cd);
+
+  pKey = tdbRealloc(*ppKey, cd.kLen);
+  if (pKey == NULL) {
+    return -1;
+  }
+
+  *ppKey = pKey;
+  *kLen = cd.kLen;
+  memcpy(pKey, cd.pKey, cd.kLen);
+
+  if (ppVal) {
+    // TODO: vLen may be zero
+    pVal = tdbRealloc(*ppVal, cd.vLen);
+    if (pVal == NULL) {
+      tdbFree(pKey);
+      return -1;
+    }
+
+    *ppVal = pVal;
+    *vLen = cd.vLen;
+    memcpy(pVal, cd.pVal, cd.vLen);
+  }
+
+  ret = tdbBtcMoveToPrev(pBtc);
+  if (ret < 0) {
+    ASSERT(0);
+    return -1;
+  }
+
+  return 0;
+}
+
 int tdbBtcMoveToNext(SBTC *pBtc) {
   int    nCells;
   int    ret;
diff --git a/source/libs/tdb/src/db/tdbTable.c b/source/libs/tdb/src/db/tdbTable.c
index 239aa5d7ef..1575f9f206 100644
--- a/source/libs/tdb/src/db/tdbTable.c
+++ b/source/libs/tdb/src/db/tdbTable.c
@@ -132,6 +132,10 @@ int tdbTbcNext(TBC *pTbc, void **ppKey, int *kLen, void **ppVal, int *vLen) {
   return tdbBtreeNext(&pTbc->btc, ppKey, kLen, ppVal, vLen);
 }
 
+int tdbTbcPrev(TBC *pTbc, void **ppKey, int *kLen, void **ppVal, int *vLen) {
+  return tdbBtreePrev(&pTbc->btc, ppKey, kLen, ppVal, vLen);
+}
+
 int tdbTbcUpsert(TBC *pTbc, const void *pKey, int nKey, const void *pData, int nData, int insert) {
   return tdbBtcUpsert(&pTbc->btc, pKey, nKey, pData, nData, insert);
 }
diff --git a/source/libs/tdb/src/inc/tdbInt.h b/source/libs/tdb/src/inc/tdbInt.h
index 6524e3c9bc..71e009cabf 100644
--- a/source/libs/tdb/src/inc/tdbInt.h
+++ b/source/libs/tdb/src/inc/tdbInt.h
@@ -156,6 +156,7 @@ int tdbBtcMoveToLast(SBTC *pBtc);
 int tdbBtcMoveToNext(SBTC *pBtc);
 int tdbBtcMoveToPrev(SBTC *pBtc);
 int tdbBtreeNext(SBTC *pBtc, void **ppKey, int *kLen, void **ppVal, int *vLen);
+int tdbBtreePrev(SBTC *pBtc, void **ppKey, int *kLen, void **ppVal, int *vLen);
 int tdbBtcGet(SBTC *pBtc, const void **ppKey, int *kLen, const void **ppVal, int *vLen);
 int tdbBtcDelete(SBTC *pBtc);
 int tdbBtcUpsert(SBTC *pBtc, const void *pKey, int kLen, const void *pData, int nData, int insert);
diff --git a/tests/script/tsim/stable/alter_comment.sim b/tests/script/tsim/stable/alter_comment.sim
index cfcbb9a1da..19f4858585 100644
--- a/tests/script/tsim/stable/alter_comment.sim
+++ b/tests/script/tsim/stable/alter_comment.sim
@@ -159,7 +159,7 @@ sql alter table db.stb rename tag t1 tx
 
 print ========== alter common
 sql alter table db.stb comment 'abcde' ;
-sql alter table db.stb ttl 10 ;
+sql_error alter table db.stb ttl 10 ;
 
 sql show db.stables;
 if $data[0][6] != abcde then
diff --git a/tests/system-test/2-query/ttl_comment.py b/tests/system-test/2-query/ttl_comment.py
new file mode 100644
index 0000000000..8fc582c587
--- /dev/null
+++ b/tests/system-test/2-query/ttl_comment.py
@@ -0,0 +1,206 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, db_test.stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+import taos
+from util.log import tdLog
+from util.cases import tdCases
+from util.sql import tdSql
+
+class TDTestCase:
+    def caseDescription(self):
+        '''
+        ttl/comment test
+        '''
+        return
+
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.error("create table ttl_table1(ts timestamp, i int) ttl 1.1")
+        tdSql.error("create table ttl_table2(ts timestamp, i int) ttl 1e1")
+        tdSql.error("create table ttl_table3(ts timestamp, i int) ttl -1")
+
+        print("============== STEP 1 ===== test normal table")
+
+        tdSql.execute("create table normal_table1(ts timestamp, i int)")
+        tdSql.execute("create table normal_table2(ts timestamp, i int) comment '' ttl 3")
+        tdSql.execute("create table normal_table3(ts timestamp, i int) ttl 2100000000020 comment 'hello'")
+
+        tdSql.query("show tables like 'normal_table1'")
+        tdSql.checkData(0, 0, 'normal_table1')
+        tdSql.checkData(0, 7, 0)
+        tdSql.checkData(0, 8, None)
+
+
+        tdSql.query("show tables like 'normal_table2'")
+        tdSql.checkData(0, 0, 'normal_table2')
+        tdSql.checkData(0, 7, 3)
+        tdSql.checkData(0, 8, '')
+
+
+        tdSql.query("show tables like 'normal_table3'")
+        tdSql.checkData(0, 0, 'normal_table3')
+        tdSql.checkData(0, 7, 2147483647)
+        tdSql.checkData(0, 8, 'hello')
+
+        tdSql.execute("alter table normal_table1 comment 'nihao'")
+        tdSql.query("show tables like 'normal_table1'")
+        tdSql.checkData(0, 0, 'normal_table1')
+        tdSql.checkData(0, 8, 'nihao')
+
+        tdSql.execute("alter table normal_table1 comment ''")
+        tdSql.query("show tables like 'normal_table1'")
+        tdSql.checkData(0, 0, 'normal_table1')
+        tdSql.checkData(0, 8, '')
+
+        tdSql.execute("alter table normal_table2 comment 'fly'")
+        tdSql.query("show tables like 'normal_table2'")
+        tdSql.checkData(0, 0, 'normal_table2')
+        tdSql.checkData(0, 8, 'fly')
+
+        tdSql.execute("alter table normal_table3 comment 'fly'")
+        tdSql.query("show tables like 'normal_table3'")
+        tdSql.checkData(0, 0, 'normal_table3')
+        tdSql.checkData(0, 8, 'fly')
+
+        tdSql.execute("alter table normal_table1 ttl 1")
+        tdSql.query("show tables like 'normal_table1'")
+        tdSql.checkData(0, 0, 'normal_table1')
+        tdSql.checkData(0, 7, 1)
+
+        tdSql.execute("alter table normal_table3 ttl 0")
+        tdSql.query("show tables like 'normal_table3'")
+        tdSql.checkData(0, 0, 'normal_table3')
+        tdSql.checkData(0, 7, 0)
+
+
+        print("============== STEP 2 ===== test super table")
+
+        tdSql.execute("create table super_table1(ts timestamp, i int) tags(t int)")
+        tdSql.execute("create table super_table2(ts timestamp, i int) tags(t int) comment ''")
+        tdSql.execute("create table super_table3(ts timestamp, i int) tags(t int) comment 'super'")
+
+        tdSql.query("show stables like 'super_table1'")
+        tdSql.checkData(0, 0, 'super_table1')
+        tdSql.checkData(0, 6, None)
+
+
+        tdSql.query("show stables like 'super_table2'")
+        tdSql.checkData(0, 0, 'super_table2')
+        tdSql.checkData(0, 6, '')
+
+
+        tdSql.query("show stables like 'super_table3'")
+        tdSql.checkData(0, 0, 'super_table3')
+        tdSql.checkData(0, 6, 'super')
+
+
+        tdSql.execute("alter table super_table1 comment 'nihao'")
+        tdSql.query("show stables like 'super_table1'")
+        tdSql.checkData(0, 0, 'super_table1')
+        tdSql.checkData(0, 6, 'nihao')
+
+        tdSql.execute("alter table super_table1 comment ''")
+        tdSql.query("show stables like 'super_table1'")
+        tdSql.checkData(0, 0, 'super_table1')
+        tdSql.checkData(0, 6, '')
+
+        tdSql.execute("alter table super_table2 comment 'fly'")
+        tdSql.query("show stables like 'super_table2'")
+        tdSql.checkData(0, 0, 'super_table2')
+        tdSql.checkData(0, 6, 'fly')
+
+        tdSql.execute("alter table super_table3 comment 'tdengine'")
+        tdSql.query("show stables like 'super_table3'")
+        tdSql.checkData(0, 0, 'super_table3')
+        tdSql.checkData(0, 6, 'tdengine')
+
+        print("============== STEP 3 ===== test child table")
+
+        tdSql.execute("create table child_table1 using super_table1 tags(1) ttl 10")
+        tdSql.execute("create table child_table2 using super_table1 tags(1) comment ''")
+        tdSql.execute("create table child_table3 using super_table1 tags(1) comment 'child'")
+        tdSql.execute("insert into child_table4 using super_table1 tags(1) values(now, 1)")
+
+
+        tdSql.query("show tables like 'child_table1'")
+        tdSql.checkData(0, 0, 'child_table1')
+        tdSql.checkData(0, 7, 10)
+        tdSql.checkData(0, 8, None)
+
+
+        tdSql.query("show tables like 'child_table2'")
+        tdSql.checkData(0, 0, 'child_table2')
+        tdSql.checkData(0, 7, 0)
+        tdSql.checkData(0, 8, '')
+
+
+        tdSql.query("show tables like 'child_table3'")
+        tdSql.checkData(0, 0, 'child_table3')
+        tdSql.checkData(0, 8, 'child')
+
+        tdSql.query("show tables like 'child_table4'")
+        tdSql.checkData(0, 0, 'child_table4')
+        tdSql.checkData(0, 7, 0)
+        tdSql.checkData(0, 8, None)
+
+
+        tdSql.execute("alter table child_table1 comment 'nihao'")
+        tdSql.query("show tables like 'child_table1'")
+        tdSql.checkData(0, 0, 'child_table1')
+        tdSql.checkData(0, 8, 'nihao')
+
+        tdSql.execute("alter table child_table1 comment ''")
+        tdSql.query("show tables like 'child_table1'")
+        tdSql.checkData(0, 0, 'child_table1')
+        tdSql.checkData(0, 8, '')
+
+        tdSql.execute("alter table child_table2 comment 'fly'")
+        tdSql.query("show tables like 'child_table2'")
+        tdSql.checkData(0, 0, 'child_table2')
+        tdSql.checkData(0, 8, 'fly')
+
+        tdSql.execute("alter table child_table3 comment 'tdengine'")
+        tdSql.query("show tables like 'child_table3'")
+        tdSql.checkData(0, 0, 'child_table3')
+        tdSql.checkData(0, 8, 'tdengine')
+
+
+        tdSql.execute("alter table child_table4 comment 'tdengine'")
+        tdSql.query("show tables like 'child_table4'")
+        tdSql.checkData(0, 0, 'child_table4')
+        tdSql.checkData(0, 8, 'tdengine')
+
+        tdSql.execute("alter table child_table4 ttl 9")
+        tdSql.query("show tables like 'child_table4'")
+        tdSql.checkData(0, 0, 'child_table4')
+        tdSql.checkData(0, 7, 9)
+
+        tdSql.execute("alter table child_table3 ttl 9")
+        tdSql.query("show tables like 'child_table3'")
+        tdSql.checkData(0, 0, 'child_table3')
+        tdSql.checkData(0, 7, 9)
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
+
diff --git a/tests/system-test/fulltest.sh b/tests/system-test/fulltest.sh
index b5004d41ce..41004cc5a2 100755
--- a/tests/system-test/fulltest.sh
+++ b/tests/system-test/fulltest.sh
@@ -98,6 +98,7 @@ python3 ./test.py -f 2-query/stateduration.py
 python3 ./test.py -f 2-query/function_stateduration.py
 python3 ./test.py -f 2-query/statecount.py
 python3 ./test.py -f 2-query/tail.py
+python3 ./test.py -f 2-query/ttl_comment.py
 python3 ./test.py -f 2-query/distribute_agg_count.py
 python3 ./test.py -f 2-query/distribute_agg_max.py
 python3 ./test.py -f 2-query/distribute_agg_min.py