MDEV-17614 INSERT on dup key update is replication unsafe
Problem:- When mysql executes INSERT ON DUPLICATE KEY INSERT, the storage engine checks if the inserted row would generate a duplicate key error. If yes, it returns the existing row to mysql, mysql updates it and sends it back to the storage engine.When the table has more than one unique or primary key, this statement is sensitive to the order in which the storage engines checks the keys. Depending on this order, the storage engine may determine different rows to mysql, and hence mysql can update different rows.The order that the storage engine checks keys is not deterministic. For example, InnoDB checks keys in an order that depends on the order in which indexes were added to the table. The first added index is checked first. So if master and slave have added indexes in different orders, then slave may go out of sync. Solution:- Make INSERT...ON DUPLICATE KEY UPDATE unsafe while using stmt or mixed format When there is more then one unique key. Although there is two exception. 1. Auto Increment key is not counted because Innodb will get gap lock for failed Insert and concurrent insert will get a next increment value. But if user supplies auto inc value it can be unsafe. 2. Count only unique keys for which insertion is performed. So this patch also addresses the bug id #72921
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