Now that MySQL is upgraded to 8.0 RC1, let’s have a look on how we could check the workload and see if we can optimize something by adding indexes for example. The same technique can be used to find inefficient queries requiring rewriting.

The first thing we will check is some information regarding the usage of the user used for lefred.be’s website:

mysql> select * from sys.user_summary where user= 'wp_lefred'\G
*************************** 1. row ***************************
user: wp_lefred
statements: 65060
statement_latency: 2.71 m
statement_avg_latency: 2.50 ms
table_scans: 234
file_ios: 17151
file_io_latency: 54.83 s
current_connections: 0
total_connections: 2541
unique_hosts: 1
current_memory: 52.27 MiB
total_memory_allocated: 12.50 GiB

This was after the upgrade, so not much info yet but if I compare with the other sites hosted on the …

Yesterday I decided to upgrade the database server of lefred.be running the latest WordPress to MySQL 8.0.

The previous version was 5.7.19.

My dedicated server is still running on CentOS 6.x, and I had just to enable the MySQL Community 8.0 yum repository and upgrade the rpms:

# yum update mysql-community-server --enablerepo=mysql80-community

After the upgrade, I had to modify my.cnf to remove the lines related to the non regretted Query Cache:

#query_cache_type=0
 …

In this blog, I’ll look at how to do MySQL point in time recovery (PITR) correctly.

Sometimes we need to restore from a backup, and then replay the transactions that happened after the backup was taken. This is a common procedure in most disaster recovery plans, when for example you accidentally drop a table/database or run an update/delete without the “where” clause and lose data.

The usual way is to get a copy of your binlogs and use mysqlbinlog to replay those transactions. But this approach has many pitfalls that can make the whole PITR process a nightmare. Some examples:

• You need to make sure to run a single mysqlbinlog command with all related binlogs, and pipe them to mysql at once. Otherwise, if binlog.000001 creates a temporary table, and …

The following query gets data from performance_schema in MySQL and attempts to regex the digest to the list of tables in the same schema.

 SELECT d.*,  
  (SELECT group_concat(distinct TABLE_NAME) FROM information_schema.TABLES   
 WHERE table_schema = d.schema_name and d.digest_text regexp table_name) table_name  
  FROM performance_schema.events_statements_summary_by_digest d  
 WHERE d.DIGEST_TEXT regexp "^(SELECT|UPDATE|DELETE|REPLACE|INSERT|CREATE)"  
 and d.LAST_SEEN >= curdate() - interval 7 day  
 ORDER BY d.SUM_TIMER_WAIT DESC limit 10\G  

Stefan Schiele, CEO, SCT Schiele talks about how Monyog helped them run mission-critical applications smoothly and without errors.

SCT Schiele are specialists in e-commerce solutions in the B2B market. The company provides deep integrations into the merchandise business, thus enabling large clientele to increase their e-commerce revenue.

Enabling e-commerce

Today, every customer expects the websites to load faster and applications to run without lag.  When your applications perform poorly, your customers notice immediately. As Stefan Schiele puts it – “Nowadays everyone expects e-commerce systems to be available 24/7. Without continuous monitoring, this is simply unachievable.”

SCT Schiele data centre has a number of own production servers and servers on which their customers run & operate services; the company currently uses Oracle, InterSystems Caché, MySQL and MariaDB databases. To …

Notes/errata/updates for Chapter 6:
See the official book errata at http://tahaghoghi.com/LearningMySQL/errata.php – Chapter 6 includes pages 179 – 222.

Other notes:
At the end of the “Creating Tables” section (p.183-4), it says “We like using the underscore character to separate words, but that’s just a matter of style and taste; you could use underscores or dashes, or omit the word-separating formatting altogether.” While this is true, beware of using a dash, because MySQL will try to interpret “two-words”, thinking – is a minus sign. I recommend avoiding dashes for this reason (even though the book does this on page 215).

At the end of the “Collation and Character Sets” section (p.186), it says “When you’re creating a database, you can set the default character set and sort order for the database and its …

Instant ADD COLUMN for InnoDB Marko Mäkelä Wed, 10/11/2017 - 11:02

MariaDB Server 10.3.2 alpha was released this week. For InnoDB, the new features coming in MariaDB Server 10.3 include CREATE SEQUENCE which is a logical continuation of the Persistent AUTO_INCREMENT that appeared in MariaDB Server 10.2.

Perhaps one of the most important InnoDB changes coming in MariaDB Server 10.3 is Instant ADD COLUMN for InnoDB tables. The design was brainstormed in April by engineers from MariaDB Corporation, Alibaba and Tencent. A prototype was developed by Vin Chen (陈福荣) from the Tencent Game DBA Team.

What is …

Despite your very best efforts, as tables increase in size and more and more users come online, sluggish MySQL performance eventually rears its ugly head. When that happens, you may be tempted to shrug it off as part of doing business. Don’t. By understanding the mechanisms behind database slowdowns and by methodically attacking the problem, you can home in on the culprit(s) and remedy the issues in a timely manner, before your business suffers substantial losses as a result.

The purpose of this blog is to assist you in determining the cause(s) of MySQL database performance issues using a couple of built-in tools.

Why Database Performance Slows Down

It’s no secret that database performance tends to degrade over time. While it’s easy to point the finger at the number of concurrent users, table scans, and growing tables, the reality is more complex than that. The most common reason for slow database performance is …

In this blog post, I’ll discuss some of the MySQL and MariaDB default configuration differences, focusing on MySQL 5.7 and MariaDB 10.2. Percona Server for MySQL uses the same defaults as MySQL, so I will not list them separately.

MariaDB Server is a general purpose open source database, created by the founders of MySQL. MariaDB Server (referred to as MariaDB for brevity) has similar roots as Percona Server for MySQL, but is quickly diverging from MySQL compatibility and growing on its own. MariaDB has become the default installation for several operating systems (such as Red Hat Enterprise Linux/CentOS/Fedora). Changes in the default variables can make a large difference in the out-of-box …

In my previous blog post, I talked about new general tablespaces in MySQL 8.0. Recently MySQL 8.0.3-rc was released, which includes a new data dictionary. My goal is to create one million tables in MySQL and test the performance.

Background questions

Q: Why million tables in MySQL? Is it even realistic? How does this happen?

Usually, millions of tables in MySQL is a result of “a schema per customer” Software as a Service (SaaS) approach. For the purposes of customer data isolation (security) and logical data partitioning (performance), each “customer” has a dedicated schema. You can think of a WordPress hosting service (or any CMS based hosting) where each …