fix(query): fix cast function constant convert to nchar result length

source/libs/nodes/src/nodesCodeFuncs.c

@@ -2084,7 +2084,7 @@ static int32_t jsonToDatum(const SJson* pJson, void* pObj) {
         code = TSDB_CODE_OUT_OF_MEMORY;
         break;
       }
-      varDataSetLen(pNode->datum.p, pNode->node.resType.bytes - VARSTR_HEADER_SIZE);
+      varDataSetLen(pNode->datum.p, pNode->node.resType.bytes);
       if (TSDB_DATA_TYPE_NCHAR == pNode->node.resType.type) {
         char *buf = taosMemoryCalloc(1, pNode->node.resType.bytes * 2 + VARSTR_HEADER_SIZE + 1);
         if (NULL == buf) {

source/libs/parser/src/parAstCreater.c

@@ -363,10 +363,8 @@ SNode* createCastFunctionNode(SAstCreateContext* pCxt, SNode* pExpr, SDataType d
   CHECK_OUT_OF_MEM(func);
   strcpy(func->functionName, "cast");
   func->node.resType = dt;
-  if (TSDB_DATA_TYPE_BINARY == dt.type) {
-    func->node.resType.bytes += 2;
-  } else if (TSDB_DATA_TYPE_NCHAR == dt.type) {
-    func->node.resType.bytes = func->node.resType.bytes * TSDB_NCHAR_SIZE + 2;
+  if (TSDB_DATA_TYPE_NCHAR == dt.type) {
+    func->node.resType.bytes = func->node.resType.bytes * TSDB_NCHAR_SIZE;
   }
   nodesListMakeAppend(&func->pParameterList, pExpr);
   return (SNode*)func;

source/libs/scalar/src/sclfunc.c

@@ -709,6 +709,10 @@ int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutp
   int16_t outputType = GET_PARAM_TYPE(&pOutput[0]);
   int64_t outputLen  = GET_PARAM_BYTES(&pOutput[0]);
 
+  if (IS_VAR_DATA_TYPE(outputType)) {
+    outputLen += VARSTR_HEADER_SIZE;
+  }
+
   char *outputBuf = taosMemoryCalloc(outputLen * pInput[0].numOfRows, 1);
   char *output = outputBuf;
 
@@ -823,7 +827,7 @@ int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutp
         }
         //for constant conversion, need to set proper length of pOutput description
         if (len < outputLen - VARSTR_HEADER_SIZE) {
-          pOutput->columnData->info.bytes = len + VARSTR_HEADER_SIZE;
+          pOutput->columnData->info.bytes = len;
         }
         break;
       }