enh(query): improve the performance and add some todo

source/libs/executor/src/executil.c

@@ -129,6 +129,7 @@ void initGroupedResultInfo(SGroupResInfo* pGroupResInfo, SSHashObj* pHashmap, in
   void* pData = NULL;
   pGroupResInfo->pRows = taosArrayInit(10, POINTER_BYTES);
 
+  // todo avoid repeated malloc memory
   size_t  keyLen = 0;
   int32_t iter = 0;
   while ((pData = tSimpleHashIterate(pHashmap, pData, &iter)) != NULL) {

source/libs/scalar/src/scalar.c

@@ -165,10 +165,7 @@ int32_t scalarGenerateSetFromList(void **data, void *pNode, uint32_t type) {
       SCL_ERR_JRET(TSDB_CODE_QRY_OUT_OF_MEMORY);
     }
 
-    colDataDestroy(out.columnData);
-    taosMemoryFreeClear(out.columnData);
-    out.columnData = taosMemoryCalloc(1, sizeof(SColumnInfoData));
-
+    colInfoDataCleanup(out.columnData, out.numOfRows);
     cell = cell->pNext;
   }
 

source/util/src/tpagedbuf.c

@@ -30,6 +30,7 @@ struct SDiskbasedBuf {
   TdFilePtr pFile;
   int32_t   allocateId;  // allocated page id
   char*     path;        // file path
+  char*     prefix;      // file name prefix
   int32_t   pageSize;    // current used page size
   int32_t   inMemPages;  // numOfPages that are allocated in memory
   SList*    freePgList;  // free page list
@@ -48,6 +49,12 @@ struct SDiskbasedBuf {
 };
 
 static int32_t createDiskFile(SDiskbasedBuf* pBuf) {
+  if (pBuf->path[0] == '\0') { // prepare the file name when needed it
+    char path[PATH_MAX] = {0};
+    taosGetTmpfilePath(pBuf->prefix, "paged-buf", path);
+    pBuf->path = taosMemoryStrDup(path);
+  }
+
   pBuf->pFile =
       taosOpenFile(pBuf->path, TD_FILE_CREATE | TD_FILE_WRITE | TD_FILE_READ | TD_FILE_TRUNC | TD_FILE_AUTO_DEL);
   if (pBuf->pFile == NULL) {
@@ -356,10 +363,7 @@ int32_t createDiskbasedBuf(SDiskbasedBuf** pBuf, int32_t pagesize, int32_t inMem
 
   pPBuf->assistBuf = taosMemoryMalloc(pPBuf->pageSize + 2);  // EXTRA BYTES
   pPBuf->all = taosHashInit(10, fn, true, false);
-
-  char path[PATH_MAX] = {0};
-  taosGetTmpfilePath(dir, "paged-buf", path);
-  pPBuf->path = strdup(path);
+  pPBuf->prefix = (char*) dir;
 
   pPBuf->emptyDummyIdList = taosArrayInit(1, sizeof(int32_t));