October 25, 2014

High-Performance Click Analysis with MySQL

We have a lot of customers who do click analysis, site analytics, search engine marketing, online advertising, user behavior analysis, and many similar types of work.  The first thing these have in common is that they’re generally some kind of loggable event. The next characteristic of a lot of these systems (real or planned) is […]

The MySQL optimizer, the OS cache, and sequential versus random I/O

In my post on estimating query completion time, I wrote about how I measured the performance on a join between a few tables in a typical star schema data warehousing scenario. In short, a query that could take several days to run with one join order takes an hour with another, and the optimizer chose […]

Finding out largest tables on MySQL Server

Finding largest tables on MySQL instance is no brainier in MySQL 5.0+ thanks to Information Schema but I still wanted to post little query I use for the purpose so I can easily find it later, plus it is quite handy in a way it presents information:

Using CHAR keys for joins, how much is the overhead ?

I prefer to use Integers for joins whenever possible and today I worked with client which used character keys, in my opinion without a big need. I told them this is suboptimal but was challenged with rightful question about the difference. I did not know so I decided to benchmark. The results below are for […]

Getting MySQL to use full key length

There is one bug, or “missing feature” in MySQL Optimizer which may give you hard time causing performance problems which may be hard to track down, it is using only part of the index when full index can be used or using shorter index while there is longer index available. The last item is yet […]

Percona XtraDB Cluster 5.6.20-25.7 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on September 1st 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.6.20-68.0 including all the bug fixes in it, Galera Replicator 3.7, and on Codership wsrep API 25.7, Percona XtraDB Cluster 5.6.20-25.7 is now […]

When (and how) to move an InnoDB table outside the shared tablespace

In my last post, “A closer look at the MySQL ibdata1 disk space issue and big tables,” I looked at the growing ibdata1 problem under the perspective of having big tables residing inside the so-called shared tablespace. In the particular case that motivated that post, we had a customer running out of disk space in his […]

Measuring failover time for ScaleArc load balancer

ScaleArc hired Percona to benchmark failover times for the ScaleArc database traffic management software in different scenarios. We tested failover times for various clustered setups, where ScaleArc itself was the load balancer for the cluster. These tests complement other performance tests on the ScaleArc software – sysbench testing for latency and testing for WordPress acceleration. […]

Recovery after DROP & CREATE

In a very popular data loss scenario a table is dropped and empty one is created with the same name. This is because  mysqldump in many cases generates the “DROP TABLE” instruction before the “CREATE TABLE”:

If there were no subsequent CREATE TABLE the recovery would be trivial. Index_id of the PRIMARY index of […]

ALTER TABLE: Creating Index by Sort and Buffer Pool Size

Today I was looking at the ALTER TABLE performance with fast index creation and without it with different buffer pool sizes. Results are pretty interesting. I used modified Sysbench table for these tests because original table as initially created only has index on column K which initially contains only zeros, which means index is very […]