MDEV-18145 Assertion `0' failed in Item::val_native upon SELECT subquery with timestamp

mysql-test/main/type_timestamp.result

@@ -1152,5 +1152,17 @@ f
 NULL
 DROP TABLE t1;
 #
+# MDEV-18145 Assertion `0' failed in Item::val_native upon SELECT subquery with timestamp
+#
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE t2 (pk INT PRIMARY KEY) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+CREATE TABLE t3 (pk INT PRIMARY KEY, b TIMESTAMP) ENGINE=MyISAM;
+SELECT ( SELECT b FROM t1 LIMIT 1 ) AS sq FROM t2 LEFT JOIN t3 USING (pk);
+sq
+NULL
+NULL
+DROP TABLE t1, t2, t3;
+#
 # End of 10.4 tests
 #

mysql-test/main/type_timestamp.test

@@ -749,6 +749,17 @@ INSERT INTO t1 () VALUES (),();
 SELECT IF(0,t,NULL) AS f FROM t1 GROUP BY 'foo';
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-18145 Assertion `0' failed in Item::val_native upon SELECT subquery with timestamp
+--echo #
+
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE t2 (pk INT PRIMARY KEY) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+CREATE TABLE t3 (pk INT PRIMARY KEY, b TIMESTAMP) ENGINE=MyISAM;
+SELECT ( SELECT b FROM t1 LIMIT 1 ) AS sq FROM t2 LEFT JOIN t3 USING (pk);
+DROP TABLE t1, t2, t3;
+
 
 --echo #
 --echo # End of 10.4 tests

sql/item_subselect.cc

@@ -1084,7 +1084,7 @@ void Item_maxmin_subselect::no_rows_in_result()
   */
   if (parsing_place != SELECT_LIST || const_item())
     return;
-  value= (new (thd->mem_root) Item_null(thd))->get_cache(thd);
+  value= get_cache(thd);
   null_value= 0;
   was_values= 0;
   make_const();
@@ -1102,7 +1102,7 @@ void Item_singlerow_subselect::no_rows_in_result()
   */
   if (parsing_place != SELECT_LIST || const_item())
     return;
-  value= (new (thd->mem_root) Item_null(thd))->get_cache(thd);
+  value= get_cache(thd);
   reset();
   make_const();
 }