MySQL Replication Error I am getting an Error on Slave as:


  could not execute Write_rows event on table mydatabasename.atable; Duplicate entry '174465' for key 'PRIMARY', Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; the event's master log mysql-bin.000004, end_log_pos 60121977


As I am directly getting updates from master so why this happens.

How can we handle this in an effective manner so that there is no data loss on the slave.I do not want to set up the whole replication again for maintaining the data integrity.

Thanks..!
Whenever there is a 1062 error, the usual table with the problem is the actual table being updated in the query. The query should appear in the output of SHOW SLAVE STATUS\G

For example, in your error it says Duplicate entry '174465' for key 'PRIMARY'. This indicates that you should look up the value 174465 in the table you are either doing an INSERT or UPDATE. If the row does exist, can you have to decide if the query halted execution will change the row's contents. If the query will simply reproduce the exact same contents, and you believe that will be the case, you can perform one of two options:

OPTION 1

Skip the error, wait 5 seconds, and view the Slave Status. Here the 5 steps for Skipping an Error

STOP SLAVE;
SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
START SLAVE;
SELECT SLEEP(5);
SHOW SLAVE STATUS\G


When you view the Slave Status, here is what to expect


If Seconds_Behind_Master is NULL


Replication is Broken : Look for Tell-Tale Signs
If Error Number is 1062 again, Repeat the 5 steps for Skipping an Error

If Seconds_Behind_Master is a Number


Replication is running
When Seconds_Behind_Master > 0, Replication is Catching Up.
When Seconds_Behind_Master = 0, Replication is Fully Caught Up.



OPTION 2

Remove the row to allow replication to continue

Delete the row from the table on the Slave and do the following 4 Steps for Skipping an Error:

STOP SLAVE;
START SLAVE;
SELECT SLEEP(5);
SHOW SLAVE STATUS\G


At the risk of sounding redundant...

When you view the Slave Status, here is what to expect


If Seconds_Behind_Master is NULL


Replication is Broken : Look for Tell-Tale Signs
If Error Number is 1062 again, delete the row Repeat the 4 steps for Skipping an Error

If Seconds_Behind_Master is a Number


Replication is running
When Seconds_Behind_Master > 0, Replication is Catching Up.
When Seconds_Behind_Master = 0, Replication is Fully Caught Up.



What if there are just too many duplicate key issues? Here are some of my earlier posts concerning how to use MAATKIT's mk-table-checksum, mk-table-sync, pt-table-checksum, pt-table-sync:


In a MySQL Master/Slave replication, what would happen if I write to the Slave?
Fixing tables out of sync as reported by pt-table-checksum, pt-table-sync is not working
MySQL replication problem: slave has become out of sync