MDEV-22805 SIGSEGV in check_fields on UPDATE

Additional case for PS protocol: UPDATE is converted to multi-update
in mysql_multi_update_prepare().

mysql-test/suite/period/r/update.result

@@ -299,6 +299,9 @@ CREATE TABLE t1 (a INT, b DATE, c DATE, PERIOD FOR APPTIME(b, c));
 INSERT INTO t1 VALUES(1, '1999-01-01', '2018-12-12');
 UPDATE t1 FOR PORTION OF APPTIME FROM (SELECT '1999-01-01' FROM t1 WHERE a=2) TO '2018-01-01' SET a = 100;
 ERROR 42000: This version of MariaDB doesn't yet support 'updating and querying the same temporal periods table'
+set @tmp= "UPDATE t1 FOR PORTION OF APPTIME FROM (SELECT '1999-01-01' FROM t1 WHERE a=2) TO '2018-01-01' SET a = 100";
+execute immediate @tmp;
+ERROR 42000: This version of MariaDB doesn't yet support 'updating and querying the same temporal periods table'
 CREATE VIEW v1 AS SELECT * FROM t1;
 UPDATE v1 FOR PORTION OF APPTIME FROM (SELECT '1999-01-01' FROM t1 WHERE a=2) TO '2018-01-01' SET a = 100;
 ERROR 42S02: 'v1' is a view

mysql-test/suite/period/t/update.test

@@ -192,8 +192,12 @@ CREATE TABLE t1 (a INT, b DATE, c DATE, PERIOD FOR APPTIME(b, c));
 INSERT INTO t1 VALUES(1, '1999-01-01', '2018-12-12');
 
 # Without a patch the following statement crashs a server built in debug mode
+let $stmt= UPDATE t1 FOR PORTION OF APPTIME FROM (SELECT '1999-01-01' FROM t1 WHERE a=2) TO '2018-01-01' SET a = 100;
 --error ER_NOT_SUPPORTED_YET
-UPDATE t1 FOR PORTION OF APPTIME FROM (SELECT '1999-01-01' FROM t1 WHERE a=2) TO '2018-01-01' SET a = 100;
+eval $stmt;
+eval set @tmp= "$stmt";
+--error ER_NOT_SUPPORTED_YET
+execute immediate @tmp;
 
 CREATE VIEW v1 AS SELECT * FROM t1;
 --error ER_IT_IS_A_VIEW

sql/sql_update.cc

@@ -190,6 +190,13 @@ static bool check_fields(THD *thd, TABLE_LIST *table, List<Item> &items,
       my_error(ER_IT_IS_A_VIEW, MYF(0), table->table_name.str);
       return TRUE;
     }
+    if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI)
+    {
+      my_error(ER_NOT_SUPPORTED_YET, MYF(0),
+               "updating and querying the same temporal periods table");
+
+      return true;
+    }
     DBUG_ASSERT(thd->lex->sql_command == SQLCOM_UPDATE);
     for (List_iterator_fast<Item> it(items); (item=it++);)
     {