"Kris, please have a look at our database. We are running a materialized dataset processor, and on a database with about 40 GB of buffer pool and a database size of 6 GB, we are observing swapping."

Now, that is interesting. The box in question has 48 GB of memory, and indeed, hardly 6 GB of data.

CODE:mysql> select 
 -> sum(data_length+index_length)/1024/1024/1024 as gb 
 -> from tables 
 -> where table_schema not in ('information_schema', 'performance_schema', 'mysql');
+----------------+
| gb             |
+----------------+
| 5.832778930664 |
+----------------+













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"Hey, Kris! We got a connection surge on $IMPORTANT_MASTER, and a short activity drop preceding that. All other graphs are flat."



and



I am looking.
Continue reading "Enemy Action"

If you have a slave, that slave is probably running with the read-only flag set in the mysqld-section of your my.cnf. To be able to write to a read-only slave you need to be the replication SQL_THREAD or have SUPER privilege.

Since 5.0.16, it is still possible to execute CREATE TEMPORARY TABLE on a read-only slave, so CREATE TEMPORARY TABLE privilege also allows you to write to a read-only slave in a limited and controlled way.

If you want to process a lot of data in a temporary table, you are probably creating the temporary table without any indices, then INSERT ... SELECT data into it, and then ALTER TABLE ... ADD INDEX afterwards, because that is usually faster than to insert data into a table with indices. Only that you cannot ALTER TABLE a temporary table, even on a server that is not read-only - in order to run ALTER TABLE on any table, even



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Today I had to migrate the mysql database of our BugZilla Installation from an old Server to a new installation. I discovered, that obviously nobody had exercised the restoring process in quite some time, because it aborted:

#1062 - Duplicate entry '223' for key 1

The problem was caused by the 'profiles' table of BugZilla, where all users are stored.
Continue reading "Test your backups"