[td-255] refactor codes.

src/query/src/qExecutor.c

@@ -6647,7 +6647,7 @@ void freeqinfoFn(void *qhandle) {
 }
 
 void* qOpenQueryMgmt(int32_t vgId) {
-  const int32_t REFRESH_HANDLE_INTERVAL = 2; // every 2 seconds, refresh handle pool
+  const int32_t REFRESH_HANDLE_INTERVAL = 30; // every 30 seconds, refresh handle pool
 
   char cacheName[128] = {0};
   sprintf(cacheName, "qhandle_%d", vgId);

src/util/inc/tcache.h

@@ -68,8 +68,6 @@ typedef struct {
   int64_t         refreshTime;
   STrashElem *    pTrash;
   char*           name;
-//  void *          tmrCtrl;
-//  void *          pTimer;
   SCacheStatis    statistics;
   SHashObj *      pHashTable;
   __cache_free_fn_t freeFp;

src/util/src/tcache.c

@@ -573,6 +573,7 @@ void taosRemoveFromTrashCan(SCacheObj *pCacheObj, STrashElem *pElem) {
   free(pElem);
 }
 
+// TODO add another lock when scanning trashcan
 void taosTrashCanEmpty(SCacheObj *pCacheObj, bool force) {
   __cache_wr_lock(pCacheObj);