[td-14428] return correct length for both nchar and varchar type.

source/client/inc/clientInt.h

@@ -153,6 +153,7 @@ typedef struct SReqResultInfo {
   const char*    pRspMsg;
   const char*    pData;
   TAOS_FIELD*    fields;
+  TAOS_FIELD*    userFields; // the fields info that return to user
   uint32_t       numOfCols;
   int32_t*       length;
   char**         convertBuf;

source/client/src/clientEnv.c

@@ -169,6 +169,7 @@ static void doFreeReqResultInfo(SReqResultInfo *pResInfo) {
   taosMemoryFreeClear(pResInfo->row);
   taosMemoryFreeClear(pResInfo->pCol);
   taosMemoryFreeClear(pResInfo->fields);
+  taosMemoryFreeClear(pResInfo->userFields);
 
   if (pResInfo->convertBuf != NULL) {
     for (int32_t i = 0; i < pResInfo->numOfCols; ++i) {

source/client/src/clientImpl.c

@@ -228,12 +228,24 @@ void setResSchemaInfo(SReqResultInfo* pResInfo, const SSchema* pSchema, int32_t
   assert(pSchema != NULL && numOfCols > 0);
 
   pResInfo->numOfCols = numOfCols;
-  pResInfo->fields = taosMemoryCalloc(numOfCols, sizeof(pSchema[0]));
+  pResInfo->fields = taosMemoryCalloc(numOfCols, sizeof(TAOS_FIELD));
+  pResInfo->userFields = taosMemoryCalloc(numOfCols, sizeof(TAOS_FIELD));
 
   for (int32_t i = 0; i < pResInfo->numOfCols; ++i) {
     pResInfo->fields[i].bytes = pSchema[i].bytes;
     pResInfo->fields[i].type  = pSchema[i].type;
+
+    pResInfo->userFields[i].bytes = pSchema[i].bytes;
+    pResInfo->userFields[i].type  = pSchema[i].type;
+
+    if (pSchema[i].type == TSDB_DATA_TYPE_VARCHAR) {
+      pResInfo->userFields[i].bytes -= VARSTR_HEADER_SIZE;
+    } else if (pSchema[i].type == TSDB_DATA_TYPE_NCHAR) {
+      pResInfo->userFields[i].bytes = (pResInfo->userFields[i].bytes - VARSTR_HEADER_SIZE) / TSDB_NCHAR_SIZE;
+    }
+
     tstrncpy(pResInfo->fields[i].name, pSchema[i].name, tListLen(pResInfo->fields[i].name));
+    tstrncpy(pResInfo->userFields[i].name, pSchema[i].name, tListLen(pResInfo->userFields[i].name));
   }
 }
 

source/client/src/clientMain.c

@@ -146,7 +146,7 @@ TAOS_FIELD *taos_fetch_fields(TAOS_RES *res) {
   }
 
   SReqResultInfo *pResInfo = &(((SRequestObj *)res)->body.resInfo);
-  return pResInfo->fields;
+  return pResInfo->userFields;
 }
 
 TAOS_RES *taos_query(TAOS *taos, const char *sql) {