diff --git a/src/cq/src/cqMain.c b/src/cq/src/cqMain.c
index 1be7552a89..84b2c297d0 100644
--- a/src/cq/src/cqMain.c
+++ b/src/cq/src/cqMain.c
@@ -241,8 +241,12 @@ static void doCreateStream(void *param, TAOS_RES *result, int32_t code) {
   SCqObj* pObj = (SCqObj*)param;
   SCqContext* pContext = pObj->pContext;
   SSqlObj* pSql = (SSqlObj*)result;
-  pContext->dbConn = pSql->pTscObj;
+  if (atomic_val_compare_exchange_ptr(&(pContext->dbConn), NULL, pSql->pTscObj) != NULL) {
+    taos_close(pSql->pTscObj);
+  }
+  pthread_mutex_lock(&pContext->mutex);
   cqCreateStream(pContext, pObj);
+  pthread_mutex_unlock(&pContext->mutex);
 }
 
 static void cqProcessCreateTimer(void *param, void *tmrId) {
@@ -253,7 +257,9 @@ static void cqProcessCreateTimer(void *param, void *tmrId) {
     cDebug("vgId:%d, try connect to TDengine", pContext->vgId);
     taos_connect_a(NULL, pContext->user, pContext->pass, pContext->db, 0, doCreateStream, param, NULL);
   } else {
+    pthread_mutex_lock(&pContext->mutex);
     cqCreateStream(pContext, pObj);
+    pthread_mutex_unlock(&pContext->mutex);
   }
 }
 
@@ -267,12 +273,14 @@ static void cqCreateStream(SCqContext *pContext, SCqObj *pObj) {
   }
   pObj->tmrId = 0;
 
-  pObj->pStream = taos_open_stream(pContext->dbConn, pObj->sqlStr, cqProcessStreamRes, 0, pObj, NULL);
-  if (pObj->pStream) {
-    pContext->num++;
-    cInfo("vgId:%d, id:%d CQ:%s is openned", pContext->vgId, pObj->tid, pObj->sqlStr);
-  } else {
-    cError("vgId:%d, id:%d CQ:%s, failed to open", pContext->vgId, pObj->tid, pObj->sqlStr);
+  if (pObj->pStream == NULL) {
+    pObj->pStream = taos_open_stream(pContext->dbConn, pObj->sqlStr, cqProcessStreamRes, 0, pObj, NULL);
+    if (pObj->pStream) {
+      pContext->num++;
+      cInfo("vgId:%d, id:%d CQ:%s is openned", pContext->vgId, pObj->tid, pObj->sqlStr);
+    } else {
+      cError("vgId:%d, id:%d CQ:%s, failed to open", pContext->vgId, pObj->tid, pObj->sqlStr);
+    }
   }
 }
 
diff --git a/src/tsdb/src/tsdbRWHelper.c b/src/tsdb/src/tsdbRWHelper.c
index e204989b02..d9d58fccf3 100644
--- a/src/tsdb/src/tsdbRWHelper.c
+++ b/src/tsdb/src/tsdbRWHelper.c
@@ -925,6 +925,8 @@ static int tsdbInsertSuperBlock(SRWHelper *pHelper, SCompBlock *pCompBlock, int
     ASSERT(pHelper->pCompInfo->blocks[0].keyLast < pHelper->pCompInfo->blocks[1].keyFirst);
   }
 
+  ASSERT((blkIdx == pIdx->numOfBlocks -1) || (!pCompBlock->last));
+
   tsdbDebug("vgId:%d tid:%d a super block is inserted at index %d", REPO_ID(pHelper->pRepo), pHelper->tableInfo.tid,
             blkIdx);
 
@@ -1050,6 +1052,8 @@ static int tsdbUpdateSuperBlock(SRWHelper *pHelper, SCompBlock *pCompBlock, int
   pIdx->maxKey = blockAtIdx(pHelper, pIdx->numOfBlocks - 1)->keyLast;
   pIdx->hasLast = (uint32_t)blockAtIdx(pHelper, pIdx->numOfBlocks - 1)->last;
 
+  ASSERT((blkIdx == pIdx->numOfBlocks-1) || (!pCompBlock->last));
+
   tsdbDebug("vgId:%d tid:%d a super block is updated at index %d", REPO_ID(pHelper->pRepo), pHelper->tableInfo.tid,
             blkIdx);
 
@@ -1630,11 +1634,7 @@ static int tsdbProcessMergeCommit(SRWHelper *pHelper, SCommitIter *pCommitIter,
                                   pCfg->update);
 
         if (pDataCols->numOfRows == 0) break;
-        if (tblkIdx == pIdx->numOfBlocks - 1) {
-          if (tsdbWriteBlockToProperFile(pHelper, pDataCols, &compBlock) < 0) return -1;
-        } else {
-          if (tsdbWriteBlockToFile(pHelper, helperDataF(pHelper), pDataCols, &compBlock, false, true) < 0) return -1;
-        }
+        if (tsdbWriteBlockToFile(pHelper, helperDataF(pHelper), pDataCols, &compBlock, false, true) < 0) return -1;
 
         if (round == 0) {
           if (oBlock.last && pHelper->hasOldLastBlock) pHelper->hasOldLastBlock = false;
diff --git a/src/util/src/tfile.c b/src/util/src/tfile.c
index 1fa6a3d096..64fea2843b 100644
--- a/src/util/src/tfile.c
+++ b/src/util/src/tfile.c
@@ -93,17 +93,23 @@ int64_t tfRead(int64_t tfd, void *buf, int64_t count) {
   return ret;
 }
 
-int64_t tfFsync(int64_t tfd) {
+int32_t tfFsync(int64_t tfd) {
   void *p = taosAcquireRef(tsFileRsetId, tfd);
   if (p == NULL) return -1;
 
   int32_t fd = (int32_t)(uintptr_t)p;
-  return fsync(fd);
+  int32_t code = fsync(fd);
+
+  taosReleaseRef(tsFileRsetId, tfd);
+  return code;
 }
 
 bool tfValid(int64_t tfd) {
   void *p = taosAcquireRef(tsFileRsetId, tfd);
-  return p != NULL;
+  if (p == NULL) return false;
+
+  taosReleaseRef(tsFileRsetId, tfd);
+  return true;
 }
 
 int64_t tfLseek(int64_t tfd, int64_t offset, int32_t whence) {
@@ -111,7 +117,10 @@ int64_t tfLseek(int64_t tfd, int64_t offset, int32_t whence) {
   if (p == NULL) return -1;
 
   int32_t fd = (int32_t)(uintptr_t)p;
-  return taosLSeek(fd, offset, whence);
+  int64_t ret = taosLSeek(fd, offset, whence);
+
+  taosReleaseRef(tsFileRsetId, tfd);
+  return ret;
 }
 
 int32_t tfFtruncate(int64_t tfd, int64_t length) {
@@ -119,5 +128,8 @@ int32_t tfFtruncate(int64_t tfd, int64_t length) {
   if (p == NULL) return -1;
 
   int32_t fd = (int32_t)(uintptr_t)p;
-  return taosFtruncate(fd, length);
+  int32_t code = taosFtruncate(fd, length);
+
+  taosReleaseRef(tsFileRsetId, tfd);
+  return code;
 }
diff --git a/src/util/src/ttimer.c b/src/util/src/ttimer.c
index 0222a6d80a..baf396f030 100644
--- a/src/util/src/ttimer.c
+++ b/src/util/src/ttimer.c
@@ -560,6 +560,37 @@ void taosTmrCleanUp(void* handle) {
   tmrDebug("%s timer controller is cleaned up.", ctrl->label);
   ctrl->label[0] = 0;
 
+  // cancel all timers of this controller
+  for (size_t i = 0; i < timerMap.size; i++) {
+    timer_list_t* list = timerMap.slots + i;
+    lockTimerList(list);
+
+    tmr_obj_t* t = list->timers;
+    tmr_obj_t* prev = NULL;
+    while (t != NULL) {
+      tmr_obj_t* next = t->mnext;
+      if (t->ctrl != ctrl) {
+        prev = t;
+        t = next;
+        continue;
+      }
+
+      uint8_t state = atomic_val_compare_exchange_8(&t->state, TIMER_STATE_WAITING, TIMER_STATE_CANCELED);
+      if (state == TIMER_STATE_WAITING) {
+        removeFromWheel(t);
+      }
+      timerDecRef(t);
+      if (prev == NULL) {
+        list->timers = next;
+      } else {
+        prev->mnext = next;
+      }
+      t = next;
+    }
+
+    unlockTimerList(list);
+  }
+
   pthread_mutex_lock(&tmrCtrlMutex);
   ctrl->next = unusedTmrCtrl;
   numOfTmrCtrl--;