MySQL Bugs: #31151: Provide downwards compatability for replication

Bug #31151	Provide downwards compatability for replication
Submitted:	23 Sep 2007 6:43	Modified:	23 Sep 2007 17:02
Reporter:	Mark Callaghan	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S4 (Feature request)
Version:	5.0, 4.0	OS:	Any
Assigned to:	Assigned Account	CPU Architecture:	Any
Tags:	compatability, downgrade, replication, upgrade

Description:
When it is time to upgrade masters from MySQL4 to MySQL5, some customers like to keep a slave at the old MySQL version for some time after the upgrade just in case. They also want the MySQL4 slave to remain current with the master to make it possible to quickly revert the master to MySQL4 and also to allow for data quality comparisons between MySQL4 and MySQL5.

It isn't possible to do this today as a MySQL4 slave cannot connect to a MySQL5 master. This is the case even when the SQL used on the MySQL5 master is limited to that supported by MySQL4 and nothing crazy is done with character sets.

For future releases, I think this is a valuable feature for enterprise users.

How to repeat:
Install MySQL5 on a master and MySQL4 on a slave.

Suggested fix:
Provide a gateway that automates the application of binlog events and supports downwards compatability. Configuration for error handling would also be nice -- skip and log on error, halt on error.

Thank you for a reasonable feature request.