[TD-2165]<fix>: fix bugs in cancel query.

src/dnode/src/dnodeVRead.c

@@ -92,6 +92,7 @@ void dnodeDispatchToVReadQueue(SRpcMsg *pMsg) {
     pHead->vgId = htonl(pHead->vgId);
     pHead->contLen = htonl(pHead->contLen);
 
+    assert(pHead->contLen > 0);
     void *pVnode = vnodeAcquire(pHead->vgId);
     if (pVnode != NULL) {
       int32_t code = vnodeWriteToRQueue(pVnode, pCont, pHead->contLen, TAOS_QTYPE_RPC, pMsg);

src/vnode/src/vnodeRead.c

@@ -415,7 +415,7 @@ int32_t vnodeNotifyCurrentQhandle(void *handle, void *qhandle, int32_t vgId) {
   pCancelMsg->header.contLen = htonl(sizeof(SCancelQueryMsg));
 
   vDebug("QInfo:%p register qhandle to connect:%p", qhandle, handle);
-  return rpcReportProgress(handle, (char *)pCancelMsg, sizeof(SRetrieveTableMsg));
+  return rpcReportProgress(handle, (char *)pCancelMsg, sizeof(SCancelQueryMsg));
 }
 
 int32_t vnodeProcessCancelMsg(SVnodeObj *pVnode, SVReadMsg *pRead) {
@@ -451,6 +451,5 @@ int32_t vnodeProcessCancelMsg(SVnodeObj *pVnode, SVReadMsg *pRead) {
   qReleaseQInfo(pVnode->qMgmt, (void **)&handle, true);
 
   vnodeBuildNoResultQueryRsp(pRet);
-  code = TSDB_CODE_TSC_QUERY_CANCELLED;
-  return code;
+  return TSDB_CODE_TSC_QUERY_CANCELLED;
 }