MDEV-30345 DML does not find rows it is supposed to

This only happens with 'timestamp_column IN (select ...)

The reason was a missing assignment in Item_cache_timestamp::cache_value()

mysql-test/main/cache_temporal_4265.result

@@ -20,3 +20,21 @@ select (select max(m2.ut) from t1 m2 where m1.id <> 0) from t1 m1;
 2001-01-01 00:00:00.200000
 2001-01-01 00:00:00.200000
 drop table t1;
+#
+# MDEV-30345 DML does not find rows it is supposed to
+#
+CREATE TABLE t1 (f timestamp);
+INSERT INTO t1 VALUES ('2022-01-01 00:00:00'),('2022-12-12 12:12:12');
+CREATE TABLE t2 (f timestamp);
+INSERT INTO t2 VALUES ('2022-01-01 00:00:00'),('2022-12-12 12:12:12');
+SELECT * FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+f
+2022-01-01 00:00:00
+2022-12-12 12:12:12
+DELETE FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+SELECT * FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+f
+DROP TABLE t1,t2;
+#
+# End of 10.4 tests
+#

mysql-test/main/cache_temporal_4265.test

@@ -20,3 +20,21 @@ select * from t1;
 select (select max(m2.ut) from t1 m2 where m1.id <> 0) from t1 m1;
 drop table t1;
 
+--echo #
+--echo # MDEV-30345 DML does not find rows it is supposed to
+--echo #
+
+CREATE TABLE t1 (f timestamp);
+INSERT INTO t1 VALUES ('2022-01-01 00:00:00'),('2022-12-12 12:12:12');
+
+CREATE TABLE t2 (f timestamp);
+INSERT INTO t2 VALUES ('2022-01-01 00:00:00'),('2022-12-12 12:12:12');
+
+SELECT * FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+DELETE FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+SELECT * FROM t2 WHERE f IN ( SELECT f FROM t1 ) ;
+DROP TABLE t1,t2;
+
+--echo #
+--echo # End of 10.4 tests
+--echo #

sql/item.cc

@@ -10225,8 +10225,8 @@ bool Item_cache_timestamp::cache_value()
   if (!example)
     return false;
   value_cached= true;
-  null_value= example->val_native_with_conversion_result(current_thd, &m_native,
-                                                         type_handler());
+  null_value_inside= null_value=
+    example->val_native_with_conversion_result(current_thd, &m_native, type_handler());
   return true;
 }