Working as MySQL DBA, you will often have to deal with schema changes. Changes to production databases are not popular among DBAs, but they are necessary when applications add new requirements on the databases. If you manage a Galera Cluster, this is even more challenging than usual - the default method of doing schema changes (Total Order Isolation) locks the whole cluster for the duration of the alter. There are two more ways to go, though - online schema change and Rolling Schema Upgrade.

A popular method of performing schema changes, using pt-online-schema-change, has its own limitations. It can be tricky if your workload consists of long running transactions, or the workload is highly concurrent and the …

Setting the correct total maximum connections of your server depends on how large your memory is. Each connection thread consumes an amount of your total memory. For example you have 4GB memory in your server and each thread is using around 2MB of RAM, a 100 concurrent connections is actually eating up a total of 200MB of your memory.

So how do we compute the max_connections?

1. First is you need to do is get the value of the following global variables. Examine and take note of their sizes. The value stored in the database is actually in bytes so you might need to convert it to Kilobytes or Megabyte or Gigabytes by dividing it to 1024

Example:

1,073,741,824 bytes
1,073,741,824 / 1024 = 1,048,576 kilobytes
1,073,741,824 /1024 / 1024 = 1,024 megabytes
1,073,741,824 / 1024 / 1024 / 1024 = 1 gigabytes

You can use the SHOW command to display …

Wed, 2016-10-26 04:51Jan Lindstrom

From MariaDB 10.1 there is a feature where the InnoDB page size can be configured to be larger than the default 16K for normal, uncompressed tables. However, there has been little performance results that show whether the page size really effects the transaction performance or response time. In this blog, we study effects of page size on three different storage devices using the same benchmark(s). These devices are:

• Traditional hard disk
• SSD (Tree Intel X25-E Extreme SSDSA2SH032 G1GN 2.5-inch 32GB SATA II SLC Internal Solid State Drive as RAID-0)
• FusionIO NVM device (ioMemory SX300-1600 with VSL driver 4.2.1 build 1137 and NVMFS 1.1.1)

Results from different devices should not be compared to each other, as there are other variables like device bandwidth and different file systems. Instead, we will look at page size effect on each device …

The MySQL Server itself

The differences between the MySQL Community Server and the MySQL Enterprise Server 5.7 are as follows as claimed by Oracle:

• The license of the MySQL Server
• Only MySQL Enterprise Edition has the Enterprise plug-ins (Thread Pool, PAM, Audit, etc.)
• Certifications and Indemnification support for the MySQL Enterprise Server
• The MySQL Community Server statically links against yaSSL and readline vs MySQL Enterprise Server OpenSSL and libedit

The license of the MySQL Server

The MySQL Community Server is licensed under the GNU General Public License version 2 whereas the MySQL Enterprise Server is under an Oracle proprietary license as you can see from the following diffs of 2 random files:

shell> diff mysql-5.7.16-linux-glibc2.5-x86_64/share/charsets/latin1.xml …

I did more CTE blogging: check it out here and here !

I’ve been wanting an easy way to play around with MySQL Cluster lately, the latest 7.5 release is now based on the MySQL 5.7 branch, so it also has the sys schema packaged, adding more areas for me to add sys integration that is more cluster specific – especially given all of the new tables that were added within ndbinfo.

There’s a couple of examples of docker images that wrap older MySQL Cluster packages out there, but:

• Nothing up to date, I wanted to use MySQL Cluster 7.5.4
• Nothing that uses docker networks, rather than the old link style
• Nothing that helps to orchestrate starting the containers, I don’t want anything fancy, just to start a Cluster of a certain shape (n of …

Here is the third in a series of posts about CTEs, a new feature of MySQL 8.0, available in this Labs release. In the first post we had explored the new SQL syntax, and in the second we had applied it to generating series.…

Disk space issues are common, and they’re often difficult to solve quickly. One way to recover some space is by enabling InnoDB compression.

First, of course, you want to make sure you’ve covered alternative solutions. Can you archive data? Do partitioning/sharding? These generally involve application changes and can take longer.

You may need to first do conversion to InnoDB.

While compression is available for MyISAM via myisampack, and this can be useful for some use cases (for example, if you are rotating out tables on a monthly basis), it makes the tables read-only, so generally you will want to first convert MyISAM tables to InnoDB.

Things to watch for in the schema: After working on functional and performance issues with full-text indexes after conversion to InnoDB, I wouldn’t recommend it. Application changes are also required to rewrite queries. You can consider outsourcing these to a tool …

InnoDBOnline buffer pool resize:

• Configure innodb_buffer_pool_size offline (at startup) or online, while the server is running 

• The operation is performed in chunks

• Chunk size is defined by the innodb_buffer_pool_chunk_size configuration option      

• Buffer pool size always be equal to or a multiple of innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances

• Default innodb_buffer_pool_chunk_size is 128M

Reference:


https://dev.mysql.com/doc/refman/5.7/en/innodb-buffer-pool-resize.html



Online RENAME INDEX operation:

• ALTER TABLE RENAME INDEX requires only meta-data change.

Reference:

…

Prepare the RPM repository server

Install the software to create a RPM repository server (on an Ubuntu web server):

shell> sudo apt-get install createrepo

Create the directory structures and initialize the repositories:

shell> sudo mkdir -p /var/www/html/repos/centos/7/os/x86_64
shell> sudo createrepo /var/www/html/repos/centos/7/os/x86_64/

Copy the MySQL Enterprise RPM packages to the repository:

shell> sudo cd /var/www/html/repos/centos/7/os/x86_64/
shell> sudo unzip -v /download/V790254-01.zip   # MySQL Enterprise Server 5.7.16
Archive:  /download/V790254-01.zip
   Length  Method      Size Cmpr    Date    Time   CRC-32   Name
---------  ------  -------- ---- ---------- ----- --------  ----
 23979568  Stored  23979568   0% 2016-09-29 16:56 ae6693b1  mysql-commercial-client-5.7.16-1.1.el7.x86_64.rpm
 45327096  Stored  45327096   0% 2016-09-29 16:56 bb83c965 …