diff --git a/include/common/tglobal.h b/include/common/tglobal.h
index 1b44b6d7ea..9b301f5d10 100644
--- a/include/common/tglobal.h
+++ b/include/common/tglobal.h
@@ -108,7 +108,7 @@ extern float   tsStreamComputDelayRatio;  // the delayed computing ration of the
 extern int64_t tsMaxRetentWindow;
 
 // build info
-extern char version[];
+extern char td_version[];
 extern char compatible_version[];
 extern char gitinfo[];
 extern char buildinfo[];
diff --git a/include/util/version.h b/include/util/version.h
index bac29e5baf..ef6bfdc182 100644
--- a/include/util/version.h
+++ b/include/util/version.h
@@ -20,7 +20,7 @@
 extern "C" {
 #endif
 
-extern char version[];
+extern char td_version[];
 extern char compatible_version[];
 extern char gitinfo[];
 extern char buildinfo[];
diff --git a/source/client/src/clientMain.c b/source/client/src/clientMain.c
index 83b481658e..bdea03520a 100644
--- a/source/client/src/clientMain.c
+++ b/source/client/src/clientMain.c
@@ -397,7 +397,7 @@ const char *taos_data_type(int type) {
   }
 }
 
-const char *taos_get_client_info() { return version; }
+const char *taos_get_client_info() { return td_version; }
 
 int taos_affected_rows(TAOS_RES *res) {
   if (res == NULL || TD_RES_TMQ(res)) {
diff --git a/source/common/src/tglobal.c b/source/common/src/tglobal.c
index fbb4f78425..68a445db6a 100644
--- a/source/common/src/tglobal.c
+++ b/source/common/src/tglobal.c
@@ -362,7 +362,7 @@ static int32_t taosAddSystemCfg(SConfig *pCfg) {
   if (cfgAddString(pCfg, "os version", info.version, 1) != 0) return -1;
   if (cfgAddString(pCfg, "os machine", info.machine, 1) != 0) return -1;
 
-  if (cfgAddString(pCfg, "version", version, 1) != 0) return -1;
+  if (cfgAddString(pCfg, "version", td_version, 1) != 0) return -1;
   if (cfgAddString(pCfg, "compatible_version", compatible_version, 1) != 0) return -1;
   if (cfgAddString(pCfg, "gitinfo", gitinfo, 1) != 0) return -1;
   if (cfgAddString(pCfg, "buildinfo", buildinfo, 1) != 0) return -1;
diff --git a/source/dnode/mgmt/exe/dmMain.c b/source/dnode/mgmt/exe/dmMain.c
index 2b0f6a01a0..05e246ffe8 100644
--- a/source/dnode/mgmt/exe/dmMain.c
+++ b/source/dnode/mgmt/exe/dmMain.c
@@ -114,7 +114,7 @@ static void dmPrintVersion() {
 #else
   char *releaseName = "community";
 #endif
-  printf("%s version: %s compatible_version: %s\n", releaseName, version, compatible_version);
+  printf("%s version: %s compatible_version: %s\n", releaseName, td_version, compatible_version);
   printf("gitinfo: %s\n", gitinfo);
   printf("buildInfo: %s\n", buildinfo);
 }
diff --git a/source/dnode/mnode/impl/src/mndMain.c b/source/dnode/mnode/impl/src/mndMain.c
index ef9276caf6..4a1f0695a9 100644
--- a/source/dnode/mnode/impl/src/mndMain.c
+++ b/source/dnode/mnode/impl/src/mndMain.c
@@ -117,7 +117,7 @@ static void *mndThreadFp(void *param) {
   setThreadName("mnode-timer");
 
   while (1) {
-    if (lastTime % (100) == 0) {   // sleep 1 day for ttl
+    if (lastTime % (864000) == 0) {   // sleep 1 day for ttl
       mndPushTtlTime(pMnode);
     }
 
@@ -642,7 +642,7 @@ int32_t mndGetMonitorInfo(SMnode *pMnode, SMonClusterInfo *pClusterInfo, SMonVgr
   }
 
   // cluster info
-  tstrncpy(pClusterInfo->version, version, sizeof(pClusterInfo->version));
+  tstrncpy(pClusterInfo->version, td_version, sizeof(pClusterInfo->version));
   pClusterInfo->monitor_interval = tsMonitorInterval;
   pClusterInfo->connections_total = mndGetNumOfConnections(pMnode);
 
diff --git a/source/dnode/mnode/impl/src/mndProfile.c b/source/dnode/mnode/impl/src/mndProfile.c
index 4cfcf389aa..f5a046ae52 100644
--- a/source/dnode/mnode/impl/src/mndProfile.c
+++ b/source/dnode/mnode/impl/src/mndProfile.c
@@ -232,7 +232,7 @@ static int32_t mndProcessConnectReq(SRpcMsg *pReq) {
   connectRsp.connType = connReq.connType;
   connectRsp.dnodeNum = mndGetDnodeSize(pMnode);
 
-  snprintf(connectRsp.sVersion, sizeof(connectRsp.sVersion), "ver:%s\nbuild:%s\ngitinfo:%s", version, buildinfo,
+  snprintf(connectRsp.sVersion, sizeof(connectRsp.sVersion), "ver:%s\nbuild:%s\ngitinfo:%s", td_version, buildinfo,
            gitinfo);
   mndGetMnodeEpSet(pMnode, &connectRsp.epSet);
 
diff --git a/source/dnode/mnode/impl/src/mndStb.c b/source/dnode/mnode/impl/src/mndStb.c
index 9c45fa352f..e0e3166e28 100644
--- a/source/dnode/mnode/impl/src/mndStb.c
+++ b/source/dnode/mnode/impl/src/mndStb.c
@@ -280,7 +280,7 @@ static int32_t mndStbActionUpdate(SSdb *pSdb, SStbObj *pOld, SStbObj *pNew) {
     }
   }
 
-  if (pOld->commentLen < pNew->commentLen) {
+  if (pOld->commentLen < pNew->commentLen && pNew->commentLen > 0) {
     void *comment = taosMemoryMalloc(pNew->commentLen + 1);
     if (comment != NULL) {
       taosMemoryFree(pOld->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);
@@ -325,7 +326,7 @@ static int32_t mndStbActionUpdate(SSdb *pSdb, SStbObj *pOld, SStbObj *pNew) {
   pOld->numOfTags = pNew->numOfTags;
   memcpy(pOld->pColumns, pNew->pColumns, pOld->numOfColumns * sizeof(SSchema));
   memcpy(pOld->pTags, pNew->pTags, pOld->numOfTags * sizeof(SSchema));
-  if (pNew->commentLen != 0) {
+  if (pNew->commentLen > 0) {
     memcpy(pOld->comment, pNew->comment, pNew->commentLen + 1);
   }
   if (pNew->ast1Len != 0) {
diff --git a/source/dnode/mnode/impl/src/mndTelem.c b/source/dnode/mnode/impl/src/mndTelem.c
index 27814fe5be..d11e0c214f 100644
--- a/source/dnode/mnode/impl/src/mndTelem.c
+++ b/source/dnode/mnode/impl/src/mndTelem.c
@@ -110,7 +110,7 @@ static char* mndBuildTelemetryReport(SMnode* pMnode) {
   snprintf(tmp, sizeof(tmp), "%" PRId64 " kB", tsTotalMemoryKB);
   tjsonAddStringToObject(pJson, "memory", tmp);
 
-  tjsonAddStringToObject(pJson, "version", version);
+  tjsonAddStringToObject(pJson, "version", td_version);
   tjsonAddStringToObject(pJson, "buildInfo", buildinfo);
   tjsonAddStringToObject(pJson, "gitInfo", gitinfo);
   tjsonAddStringToObject(pJson, "email", pMgmt->email);
diff --git a/source/dnode/vnode/src/meta/metaTable.c b/source/dnode/vnode/src/meta/metaTable.c
index 4d53059957..bf5d5912f9 100644
--- a/source/dnode/vnode/src/meta/metaTable.c
+++ b/source/dnode/vnode/src/meta/metaTable.c
@@ -400,8 +400,8 @@ static void metaBuildTtlIdxKey(STtlIdxKey *ttlKey, const SMetaEntry *pME){
 
   if (ttlDays <= 0) return;
 
-//  ttlKey->dtime = ctime / 1000 + ttlDays * 24 * 60 * 60;
-  ttlKey->dtime = ctime / 1000 + ttlDays;
+  ttlKey->dtime = ctime / 1000 + ttlDays * 24 * 60 * 60;
+//  ttlKey->dtime = ctime / 1000 + ttlDays;
   ttlKey->uid = pME->uid;
 }
 
@@ -499,7 +499,6 @@ static int metaAlterTableColumn(SMeta *pMeta, int64_t version, SVAlterTbReq *pAl
   tDecoderInit(&dc, entry.pBuf, nData);
   ret = metaDecodeEntry(&dc, &entry);
   ASSERT(ret == 0);
-  tDecoderClear(&dc);
 
   if (entry.type != TSDB_NORMAL_TABLE) {
     terrno = TSDB_CODE_VND_INVALID_TABLE_ACTION;
@@ -597,12 +596,16 @@ static int metaAlterTableColumn(SMeta *pMeta, int64_t version, SVAlterTbReq *pAl
   if (pNewSchema) taosMemoryFree(pNewSchema);
   tdbTbcClose(pTbDbc);
   tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
+
   return 0;
 
 _err:
   if (entry.pBuf) taosMemoryFree(entry.pBuf);
   tdbTbcClose(pTbDbc);
   tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
+
   return -1;
 }
 
@@ -800,7 +803,6 @@ static int metaUpdateTableOptions(SMeta *pMeta, int64_t version, SVAlterTbReq *p
   tDecoderInit(&dc, entry.pBuf, nData);
   ret = metaDecodeEntry(&dc, &entry);
   ASSERT(ret == 0);
-  tDecoderClear(&dc);
 
   entry.version = version;
   metaWLock(pMeta);
@@ -834,6 +836,7 @@ static int metaUpdateTableOptions(SMeta *pMeta, int64_t version, SVAlterTbReq *p
 
   tdbTbcClose(pTbDbc);
   tdbTbcClose(pUidIdxc);
+  tDecoderClear(&dc);
   if (entry.pBuf) taosMemoryFree(entry.pBuf);
   return 0;
 }
diff --git a/source/libs/function/src/udfd.c b/source/libs/function/src/udfd.c
index 02c485fa83..4d648539a9 100644
--- a/source/libs/function/src/udfd.c
+++ b/source/libs/function/src/udfd.c
@@ -785,7 +785,7 @@ static void udfdPrintVersion() {
 #else
   char *releaseName = "community";
 #endif
-  printf("%s version: %s compatible_version: %s\n", releaseName, version, compatible_version);
+  printf("%s version: %s compatible_version: %s\n", releaseName, td_version, compatible_version);
   printf("gitinfo: %s\n", gitinfo);
   printf("buildInfo: %s\n", buildinfo);
 }
diff --git a/source/libs/parser/src/parAstCreater.c b/source/libs/parser/src/parAstCreater.c
index f2f8b164ee..b2a36f9af5 100644
--- a/source/libs/parser/src/parAstCreater.c
+++ b/source/libs/parser/src/parAstCreater.c
@@ -895,9 +895,15 @@ 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;
diff --git a/source/libs/parser/src/parTranslater.c b/source/libs/parser/src/parTranslater.c
index 2a559b4864..dae5d08fdd 100644
--- a/source/libs/parser/src/parTranslater.c
+++ b/source/libs/parser/src/parTranslater.c
@@ -2810,9 +2810,6 @@ 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);
   }
@@ -4995,11 +4992,8 @@ 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){
diff --git a/source/util/src/version.c.in b/source/util/src/version.c.in
index be1a4a4048..4d00ba90c0 100644
--- a/source/util/src/version.c.in
+++ b/source/util/src/version.c.in
@@ -1,4 +1,4 @@
-char version[12] = "${TD_VER_NUMBER}";
+char td_version[12] = "${TD_VER_NUMBER}";
 char compatible_version[12] = "${TD_VER_COMPATIBLE}";
 char gitinfo[48] = "${TD_VER_GIT}";
 char buildinfo[64] = "Built at ${TD_VER_DATE}";
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..f303b67907
--- /dev/null
+++ b/tests/system-test/2-query/ttl_comment.py
@@ -0,0 +1,181 @@
+###################################################################
+#           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)")
+        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.query("show tables like 'child_table1'")
+        tdSql.checkData(0, 0, 'child_table1')
+        tdSql.checkData(0, 8, None)
+
+
+        tdSql.query("show tables like 'child_table2'")
+        tdSql.checkData(0, 0, 'child_table2')
+        tdSql.checkData(0, 8, '')
+
+
+        tdSql.query("show tables like 'child_table3'")
+        tdSql.checkData(0, 0, 'child_table3')
+        tdSql.checkData(0, 8, 'child')
+
+
+        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')
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
+
diff --git a/tools/shell/src/shellArguments.c b/tools/shell/src/shellArguments.c
index cd6613b17a..861ae99f64 100644
--- a/tools/shell/src/shellArguments.c
+++ b/tools/shell/src/shellArguments.c
@@ -67,7 +67,7 @@ void shellPrintHelp() {
 #include <argp.h>
 #include <termio.h>
 
-const char *argp_program_version = version;
+const char *argp_program_version = td_version;
 const char *argp_program_bug_address = SHELL_EMAIL;
 
 static struct argp_option shellOptions[] = {
@@ -342,7 +342,7 @@ int32_t shellParseArgs(int32_t argc, char *argv[]) {
   shell.info.promptHeader = "taos> ";
   shell.info.promptContinue = "   -> ";
   shell.info.promptSize = 6;
-  snprintf(shell.info.programVersion, sizeof(shell.info.programVersion), "version: %s", version);
+  snprintf(shell.info.programVersion, sizeof(shell.info.programVersion), "version: %s", td_version);
 
 #if defined(_TD_WINDOWS_64) || defined(_TD_WINDOWS_32)
   shell.info.osname = "Windows";
diff --git a/tools/shell/src/shellUtil.c b/tools/shell/src/shellUtil.c
index 1529ac0e52..fecb112896 100644
--- a/tools/shell/src/shellUtil.c
+++ b/tools/shell/src/shellUtil.c
@@ -68,7 +68,7 @@ int32_t shellCheckIntSize() {
   return 0;
 }
 
-void shellPrintVersion() { printf("version: %s\n", version); }
+void shellPrintVersion() { printf("version: %s\n", td_version); }
 
 void shellGenerateAuth() {
   char secretEncrypt[TSDB_PASSWORD_LEN + 1] = {0};