diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 0c31a01be6..695ce55965 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -2444,7 +2444,11 @@ static void doSendQueryReqs(SSchedMsg* pSchedMsg) {
   SSqlObj* pSql = pSchedMsg->ahandle;
   SPair* p = pSchedMsg->msg;
 
-  for(int32_t i = p->first; i < p->second; ++i) {
+  for (int32_t i = p->first; i < p->second; ++i) {
+   if (i >= pSql->subState.numOfSub) {
+      tfree(p);
+      return;
+    }
     SSqlObj* pSub = pSql->pSubs[i];
     SRetrieveSupport* pSupport = pSub->param;
 
@@ -2584,7 +2588,12 @@ int32_t tscHandleMasterSTableQuery(SSqlObj *pSql) {
   int32_t numOfTasks = (pState->numOfSub + MAX_REQUEST_PER_TASK - 1)/MAX_REQUEST_PER_TASK;
   assert(numOfTasks >= 1);
 
-  int32_t num = (pState->numOfSub/numOfTasks) + 1;
+  int32_t num;
+  if (pState->numOfSub / numOfTasks == MAX_REQUEST_PER_TASK) {
+    num = MAX_REQUEST_PER_TASK;
+  } else {
+    num = pState->numOfSub / numOfTasks + 1;
+  }
   tscDebug("0x%"PRIx64 " query will be sent by %d threads", pSql->self, numOfTasks);
 
   for(int32_t j = 0; j < numOfTasks; ++j) {