The problemSometime back a member of the MySQL support team informed us that the slaves are very sluggish, when he tried to run a delete query on the master. "What may be the problem?" we wondered. This is in RBR and its pretty usual that we have slower slaves when using RBR as compared to SBR. We requested for some more details and found that it is something else. It's a problem when a lot of rows are getting modified in a table without PRIMARY KEY.

"UPDATE t1 set a = a+1;" and other queries such as this are generally found to make slaves sluggish if the table does not have proper index. Is it a problem with the fact that a lot of data is being transferred over the network? After all the total amount of data that will be transferred over the network will be more than twice (before and after image + some header) the sizeof data that is modified. Could this be …