[XML] fix count() failed

src/sql/engine/expr/ob_expr_extract_value.cpp

@@ -70,6 +70,8 @@ int ObExprExtractValue::calc_result_typeN(ObExprResType &type,
     if (OB_SUCC(ret)) {
       type.set_type(ObVarcharType);
       type.set_collation_type(CS_TYPE_UTF8MB4_BIN);
+      // length == OB_MAX_ORACLE_VARCHAR_LENGTH is not supported by generated key, use OB_MAX_VARCHAR_LENGTH_KEY instead
+      type.set_length(OB_MAX_VARCHAR_LENGTH_KEY);
     }
   }
   return ret;

src/sql/engine/expr/ob_expr_sys_makexml.cpp

@@ -24,7 +24,7 @@ namespace sql
 {
 // Internal expression used for generate xmltype data from blob or udt with schema
 ObExprSysMakeXML::ObExprSysMakeXML(ObIAllocator &alloc)
-    : ObFuncExprOperator(alloc, T_FUN_SYS_MAKEXML, N_SYS_MAKEXML, MORE_THAN_ONE, NOT_VALID_FOR_GENERATED_COL, NOT_ROW_DIMENSION)
+    : ObFuncExprOperator(alloc, T_FUN_SYS_MAKEXML, N_SYS_MAKEXML, MORE_THAN_ONE, VALID_FOR_GENERATED_COL, NOT_ROW_DIMENSION)
 {
 }