By Giuseppe Maxia on Oct 14, 2008
MySQL 5.1.29, the next (and last) release candidate, will revert the default replication mode to STATEMENT based. As noted in Bug#39812, MIXED mode won't be the default anymore. But the template option files provided with the distribution will have a line that enables MIXED mode.
The rationale for this change is that MIXED mode as default may break existing applications, where statements like the following are used:
UPDATE t1 SET a=1 WHERE @@server_id = 1; INSERT INTO t1 (origin, val) @@server_id , 1;
We know that several users are exploiting the quirks of STATEMENT based replication to their advantage. So we decided that it was safer not to force MIXED mode on users who are upgrading.
Instead, we added MIXED mode to the option files templates, to encourage new users to start with MIXED mode.
We are very eager to boost the adoption of MIXED base replication, but we are also concerned about mismatches and would like to avoid unpleasant surprises for users who switch from 5.0 to 5.1.
Please notice that this change is not aiming at making MySQL 5.1 master servers compatible with 5.0 slaves. The manual warns explicitly against using lesser versions for slave servers, and the rationale of this change has nothing to share with mixed versions usage.
Update : fixed the master/slave mixup.