Category Archives: mysql

On performance schemas

You should probably read Marc Alff’s post about configuring Performance Schema in MySQL 5.6. We wrote another guide, how to start using user/table/index statistics first introduced in Google patch, now part of various MySQL branches and forks: Start MySQL

Posted in mysql | 3 Comments

The saddest bug of them all (SQL is dead?)

From time to time I will observe servers wasting lots of CPU when doing batch row operations. In perf top it will look like this: 8.24% mysqld [.] Arg_comparator::compare_int_unsigned() 7.17% mysqld [.] Item_cond_and::val_int() 4.37% mysqld [.] Item_field::val_int() 4.37% mysqld [.] … Continue reading

Posted in mysql | Tagged | 16 Comments

on wikipedia and mariadb

There’s some media coverage about Wikipedia switching to MariaDB, I just wanted to point out that performance figures cited are somewhat incorrect and don’t attribute gains to correct authors. Proper performance evaluation should include not just MariaDB 5.5 but Oracle’s … Continue reading

Posted in mysql, wikitech | 20 Comments

on seconds_behind_master sleuthing

With large enough infrastructure it gets a bit more and more complicated to detect whether an incident or a problem is real systems problem or a monitoring glitch. This is a story of one such investigation. With a sufficiently large … Continue reading

Posted in mysql | 1 Comment

replication prefetching revisited

Been a while since I wrote about replication work we did. Fake changes based approach was huge success, and now our prefetching has lots of coverage, where standard SELECTs cannot reach. We’re running our systems at replication pressure, where not … Continue reading

Posted in facebook, mysql

MySQL is bazillion times faster than MemSQL

I don’t like stupid benchmarks, as they waste my time. I don’t like stupid marketing, as it wastes my time too. Sometimes I succumb to those things, and now in return I want to waste your time a bit. So, … Continue reading

Posted in mysql | 27 Comments

On binlogs and datacenters

Once MySQL is deployed inside a datacenter environment (i.e. forms a cloud ;-), major feature in it becomes replication. It is used to maintain hot copies, standby copies, read-only copies, invalidate external systems, replicate to external systems, etc. If this … Continue reading

Posted in mysql | Tagged , | 1 Comment