refactor: optimize the build block perf.

include/common/tdatablock.h

@@ -184,6 +184,7 @@ static FORCE_INLINE void colDataAppendDouble(SColumnInfoData* pColumnInfoData, u
 int32_t getJsonValueLen(const char* data);
 
 int32_t colDataAppend(SColumnInfoData* pColumnInfoData, uint32_t currentRow, const char* pData, bool isNull);
+int32_t colDataReserve(SColumnInfoData* pColumnInfoData, size_t newSize);
 int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, int32_t* capacity,
                         const SColumnInfoData* pSource, int32_t numOfRow2);
 int32_t colDataAssign(SColumnInfoData* pColumnInfoData, const SColumnInfoData* pSource, int32_t numOfRows,

source/common/src/tdatablock.c

@@ -118,6 +118,28 @@ int32_t colDataAppend(SColumnInfoData* pColumnInfoData, uint32_t currentRow, con
   return 0;
 }
 
+int32_t colDataReserve(SColumnInfoData* pColumnInfoData, size_t newSize) {
+  if (!IS_VAR_DATA_TYPE(pColumnInfoData->info.type)) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  if (pColumnInfoData->varmeta.allocLen >= newSize) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  if (pColumnInfoData->varmeta.allocLen < newSize) {
+    char* buf = taosMemoryRealloc(pColumnInfoData->pData, newSize);
+    if (buf == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+
+    pColumnInfoData->pData = buf;
+    pColumnInfoData->varmeta.allocLen = newSize;
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
 static void doBitmapMerge(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, const SColumnInfoData* pSource,
                           int32_t numOfRow2) {
   if (numOfRow2 <= 0) return;

source/libs/executor/src/scanoperator.c

@@ -399,8 +399,15 @@ int32_t addTagPseudoColumnData(SReadHandle* pHandle, SExprInfo* pPseudoExpr, int
       const char* p = metaGetTableTagVal(&mr.me, pColInfoData->info.type, &tagVal);
 
       char* data = NULL;
+      int32_t len = 0;
       if (pColInfoData->info.type != TSDB_DATA_TYPE_JSON && p != NULL) {
         data = tTagValToData((const STagVal*)p, false);
+        len = varDataTLen(data);
+        code = colDataReserve(pColInfoData, len * pBlock->info.rows);
+        if (code != TSDB_CODE_SUCCESS) {
+          terrno = code;
+          return code;
+        }
       } else {
         data = (char*)p;
       }

source/libs/scalar/src/sclfunc.c

@@ -1728,6 +1728,7 @@ int32_t qTbnameFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pO
   char str[TSDB_TABLE_FNAME_LEN + VARSTR_HEADER_SIZE] = {0};
   metaGetTableNameByUid(pInput->param, uid, str);
 
+  colDataReserve(pOutput->columnData, varDataTLen(str) * (pInput->numOfRows + pOutput->numOfRows));
   for(int32_t i = 0; i < pInput->numOfRows; ++i) {
     colDataAppend(pOutput->columnData, pOutput->numOfRows + i, str, false);
   }