In my previous post, I’ve showed how to use Dtrace to find queries creating disk temporary tables (only available for OS with dtrace: solaris, freebsd, etc).

In MySQL 5.6 (which is not released yet, use “labs” version for now) we can use new performance_schema table events_statements_history or events_statements_history_long to find all performance metrics for all queries including created disk/memory tables, use of index, etc. WOW! This is what I have been waiting for a long time!

To illustrate, I have grabbed mysql-5.6.3-labs-performance-schema-linux2.6-x86_64.tar.gz from labs.mysql.com (this feature is only in labs version) and run sysbench readonly test (you need to disable prepared statements in sysbench, seems to be not working with …

For all those in New York this is an upcoming MySQL presentation held in conjunction with our colleagues at General Assembly on March 22nd 2011.

This presentation “How Better Indexes Save You Money” will be discussing how one simple technique can result in huge MySQL performance improvements and with zero code changes necessary. Many people think they know indexes, however MySQL and MySQL Storage Engines have some specifics that differ from more traditional RDBMS products. Learn some of the key analysis and verification techniques and be able to see immediate potential results in performance.

You can find more details at Meetup.com EffectiveMySQL. This new group is all about highly technical MySQL related content “no fluff, just stuff”.

Loose index scan in MySQL can really help optimizing “group by” queries in some cases (for example, if you have only min() and/or max() as your aggregate functions). For example, if you have this query (to find maximum delay for all US flights with departure on Sundays in 2010):

select max(DepDelayMinutes),       carrier, dayofweek 
from ontime_2010 
where dayofweek = 7 
group by Carrier,  dayofweek

the usual case will be adding a covered index on (dayofweek, Carrier, DepDelayMinutes). And MySQL will use this index fine (using index mean it will use the covered index):

mysql> explain select max(DepDelayMinutes), Carrier, dayofweek from ontime_2010 
where dayofweek =7 group by Carrier, dayofweek\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: ontime_2010
         type: ref
possible_keys: covered
          key: covered
      key_len: 2
          ref: const …

Here’s a sneak peek at a video matrix — this is all the videos that include Pythian Group employees at the MySQL conference. I hope to have all the rest of the videos processed and uploaded within 24 hours, with a matrix similar to the one below (but of course with many more sessions).

Sometimes we have a lots of small and rather fast queries which use group by/order by, thus creating temporary tables. Some of those queries are retrieving text fields and mysql have to use disk (myisam) temporary tables. Those queries usually run for less than 1-2 seconds, so they did not get into slow query log, however, they sometimes add serious load on the system.

Here is the stat example:

bash-3.00$  /usr/local/mysql/bin/mysqladmin -uroot -p -i 2 -r extended-status|grep tmp_disk
...
| Created_tmp_disk_tables           | 109           |
| Created_tmp_disk_tables           | 101           |
| Created_tmp_disk_tables           | 122           |
...

40-50 tmp_disk_tables created per second

So, how can we grab those queries? Usually we have to temporary enable general log, filter out queries with “group by/order by” and profile them all. On solaris/mac we can use dtrace instead.

Here is the simple script, …

Reporting queries (I will use this term here) are the queries which summaries and groups data over the certain period of time. For example, in Social Network site we want to know how many messages have been sent for the given period of time, group by region and status (sent, received, etc), order by number of messages sent.

As an example I will take a table which is used to send SMS (text messages).

SQL: select concat('+', substring(region_code,1 ,2), 'xxx') as reg, status, count(*) as cnt
from messages
where submition_date between '2009-01-01' and '2009-04-01' group by reg, status
having cnt>100 order by cnt desc, status limit 100;

This query will do a range scan over the submition_date and perform a filesort. There are common well known approaches which can be used to optimize table (“covered index”, “summary tables”, using external data warehouse, etc). …

Revision: 8 - Last Update: September 03 2008

This is the first part of a series of short articles with a how-to approach about MySQL® Performance Monitoring, Tuning & Auditing. We will see the question from a GUI prospective. In particular we will describe which monitoring-oriented features HoneyMonitor, a GUI for MySQL® currently in alpha development, implements.

I will explain how HoneyMonitor let you

1. install an audit database on your server, without the need of using 3th Party Agents nor using remote repository databases
2. enable the auditing and start monitoring your server
3. tuning your server changing a few suggested list of variables to get better performance.

We will use only the 5.1.x series of the Server as we use some Scheduled Events and the Event Scheduler has been added only in the 5.1 branch. In particular we will use MySQL® 5.1.24-rc. We will also do some …