diff --git a/src/sql/engine/expr/ob_expr_char.cpp b/src/sql/engine/expr/ob_expr_char.cpp
index f0f75b74aa..eeafb27e20 100644
--- a/src/sql/engine/expr/ob_expr_char.cpp
+++ b/src/sql/engine/expr/ob_expr_char.cpp
@@ -73,11 +73,7 @@ int ObExprChar::calc_result_typeN(ObExprResType &type, ObExprResType *types, int
       types[i].set_calc_type(ObIntType);
     }
     ObExprOperator::calc_result_flagN(type, types, param_num);
-    //set length
-    CK( OB_INVALID_COUNT != type_ctx.get_max_allowed_packet());
-    if (OB_SUCC(ret)) {
-      type.set_length(static_cast<ObLength>(type_ctx.get_max_allowed_packet()));
-    }
+    type.set_length(static_cast<ObLength>(param_num * 4 - 4));
   }
   return ret;
 }
diff --git a/src/sql/engine/expr/ob_expr_concat.cpp b/src/sql/engine/expr/ob_expr_concat.cpp
index 89e000e221..c4b55ee04a 100644
--- a/src/sql/engine/expr/ob_expr_concat.cpp
+++ b/src/sql/engine/expr/ob_expr_concat.cpp
@@ -208,6 +208,9 @@ int ObExprConcat::calc_result_typeN(ObExprResType &type,
         max_len = OB_MAX_LONGTEXT_LENGTH / 4;
       } else {
         max_len = MIN(OB_MAX_VARCHAR_LENGTH, max_len);
+        if (max_len <= 0) {
+          max_len = OB_MAX_VARCHAR_LENGTH;
+        }
       }
       type.set_length(max_len);
     }