fix(query): prepare enough buffer before convert string.

source/libs/scalar/src/sclfunc.c

@@ -707,6 +707,7 @@ int32_t substrFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOu
 
 int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput) {
   int16_t inputType  = GET_PARAM_TYPE(&pInput[0]);
+  int16_t inputLen   = GET_PARAM_BYTES(&pInput[0]);
   int16_t outputType = GET_PARAM_TYPE(&pOutput[0]);
   int64_t outputLen  = GET_PARAM_BYTES(&pOutput[0]);
 
@@ -718,15 +719,15 @@ int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutp
       colDataAppendNULL(pOutput->columnData, i);
       continue;
     }
+
     char *input = colDataGetData(pInput[0].columnData, i);
 
     switch(outputType) {
       case TSDB_DATA_TYPE_BIGINT: {
         if (inputType == TSDB_DATA_TYPE_BINARY) {
-          memcpy(output, varDataVal(input), varDataLen(input));
-          *(int64_t *)output = taosStr2Int64(output, NULL, 10);
+          *(int64_t *)output = taosStr2Int64(varDataVal(input), NULL, 10);
         } else if (inputType == TSDB_DATA_TYPE_NCHAR) {
-          char *newBuf = taosMemoryCalloc(1, outputLen * TSDB_NCHAR_SIZE + 1);
+          char *newBuf = taosMemoryCalloc(1, inputLen);
           int32_t len  = taosUcs4ToMbs((TdUcs4 *)varDataVal(input), varDataLen(input), newBuf);
           if (len < 0) {
             taosMemoryFree(newBuf);
@@ -742,10 +743,9 @@ int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutp
       }
       case TSDB_DATA_TYPE_UBIGINT: {
         if (inputType == TSDB_DATA_TYPE_BINARY) {
-          memcpy(output, varDataVal(input), varDataLen(input));
-          *(uint64_t *)output = taosStr2UInt64(output, NULL, 10);
+          *(uint64_t *)output = taosStr2UInt64(varDataVal(input), NULL, 10);
         } else if (inputType == TSDB_DATA_TYPE_NCHAR) {
-          char *newBuf = taosMemoryCalloc(1, outputLen * TSDB_NCHAR_SIZE + 1);
+          char *newBuf = taosMemoryCalloc(1, inputLen);
           int32_t len = taosUcs4ToMbs((TdUcs4 *)varDataVal(input), varDataLen(input), newBuf);
           if (len < 0) {
             taosMemoryFree(newBuf);