diff --git a/src/sql/engine/expr/ob_expr_from_unix_time.cpp b/src/sql/engine/expr/ob_expr_from_unix_time.cpp
index 438e089c21..4e30bb91fa 100644
--- a/src/sql/engine/expr/ob_expr_from_unix_time.cpp
+++ b/src/sql/engine/expr/ob_expr_from_unix_time.cpp
@@ -216,14 +216,14 @@ int ObExprFromUnixTime::eval_fromtime_normal(const ObExpr &expr,
                         usec_val))) {
       LOG_WARN("failed to get_usec_from_datum", K(ret));
       // warn on fail mode
-      ObCastMode default_cast_mode = CM_NONE;
-      if (OB_FAIL(ObSQLUtils::get_default_cast_mode(session->get_stmt_type(), session,
-                                                    default_cast_mode))) {
-        LOG_WARN("failed to get default cast mode", K(ret));
-      } else if (CM_IS_WARN_ON_FAIL(default_cast_mode)) {
+      ObCastMode cast_mode = CM_NONE;
+      int tmp_ret = OB_SUCCESS;
+      if (OB_UNLIKELY(OB_SUCCESS != (tmp_ret = ObSQLUtils::get_default_cast_mode(session->get_stmt_type(), session, cast_mode)))) {
+        LOG_WARN("get_default_cast_mode failed", K(tmp_ret), K(session->get_stmt_type()));
+      } else if (CM_IS_WARN_ON_FAIL(cast_mode)) {
         ret = OB_SUCCESS;
-        expr_datum.set_null();
       }
+      expr_datum.set_null();
     } else {
       ObTime ob_time;
       ObDatum tmp_val;
diff --git a/src/sql/engine/expr/ob_expr_timestamp_add.cpp b/src/sql/engine/expr/ob_expr_timestamp_add.cpp
index 5645173876..6bd5cf4a26 100644
--- a/src/sql/engine/expr/ob_expr_timestamp_add.cpp
+++ b/src/sql/engine/expr/ob_expr_timestamp_add.cpp
@@ -242,14 +242,14 @@ int calc_timestampadd_expr(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datu
     }
   }
   if (OB_FAIL(ret) && OB_NOT_NULL(session)) {
-    uint64_t cast_mode = 0;
-    if (OB_FAIL(ObSQLUtils::get_default_cast_mode(session->get_stmt_type(),
-            session, cast_mode))) {
-      LOG_WARN("get_default_cast_mode failed", K(ret), K(session->get_stmt_type()));
+    ObCastMode cast_mode = CM_NONE;
+    int tmp_ret = OB_SUCCESS;
+    if (OB_UNLIKELY(OB_SUCCESS != (tmp_ret = ObSQLUtils::get_default_cast_mode(session->get_stmt_type(), session, cast_mode)))) {
+      LOG_WARN("get_default_cast_mode failed", K(tmp_ret), K(session->get_stmt_type()));
     } else if (CM_IS_WARN_ON_FAIL(cast_mode)) {
       ret = OB_SUCCESS;
-      res_datum.set_null();
     }
+    res_datum.set_null();
   }
   return ret;
 }