Which databases provide the best performance when used with containers? That’s an important question for people seeking to make the most of containerized infrastructure. In this post, I take a look at some basic performance metrics for three relational databases—PostgreSQL, MySQL, and MariaDB—when they are run as containers. Introduction For the purposes of my tests, I used the official container images available from Docker Hub to install and start the databases. While the process of pulling the images and starting the containers is likely already familiar to anyone using Docker, I’ll run through the commands I used below, just so that it is clear what my process was in preparing for the performance tests. PostgreSQL To get an official Docker image with PostgreSQL, execute $ docker pull postgres To start a PostgreSQL instance: $ docker run --name postgres -d -p 127.0.0.1:5432:5432 postgres This command will start a Docker container nominated as postgres and listen to the 5432 port on localhost. The last argument is the image name. It’s very important to pass the IP and port to enable the localhost connection. To connect with PostgreSQL via the command line: $ docker run -it --rm --link postgres:postgres postgres psql -h postgres -U postgres This image has a default user (postgres) and database ready to be accessed via psql. You can use the psql interface to create and manage the database before setting the database’s configurations in your application. To connect an application with the containerized database, just set the host, port, user and database name defined in the new database. MySQL Similar to PostgreSQL, to get an official Docker image with MySQL, execute: $ docker pull mysql To start a MySQL instance: $ docker run --name mysql -p 127.0.0.1:3306:3306 -e MYSQL_ROOT_PASSWORD="password" mysql & This command will start a Docker container named mysql and listen on port 3306 on localhost. It will also be necessary to set a password that will be used to connect with the database using the default user, root. To connect with MySQL via the command line: $ docker run -it --link mysql:mysql --rm mysql sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"' You’ll need to pass host, port, and password as environment variables. MariaDB As expected, running this image is almost exactly the same as running the MySQL image. To get the official Docker image for MariaDB: $ docker pull mariadb To start a MariaDB instance: $ docker run --name mariadb -p 127.0.0.1:3306:3306 -e MYSQL_ROOT_PASSWORD=password mariadb & To connect to MySQL via the command line: $ docker run -it --link mariadb:mysql --rm mariadb sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"' [caption id=\“attachment_6023\” align=\“alignright\” width=\“210\”] Free eBook: Compare architecture, usability, and feature sets for Kubernetes, Mesos/Marathon, and Docker Swarm[/caption] Comparisons A simple and fast way to measure the performance of each of these databases when run as a container is by creating a table with an int column and inserting 1,000 records, then comparing the time that each database takes to complete the query. To do that, first create a table (this command will be the same no matter which database you are using): create function addUsers() returns void as $$ declare i int; begin for i in 1..1000 loop insert into users(id) values (i); end loop; return; end; $$ language plpgsql; Execute the PostgreSQL function with: $ select addUsers(); For MySQL and MariaDB, you can create this function to insert 1,000 users: delimiter $$ create procedure addUsers() begin declare i int default 1; while (i <= 1000) do insert into users (id) values (i); set i=i+1; end while; end$$ delimiter ; Then execute it with: $ call addUsers(); Results Now, the big question: What are the results? PostgreSQL: ~1 second MySQL: ~12.32 seconds MariaDB: ~12.71 seconds MySQL and MariaDB performed similarly, with a negligible difference. However, the PostgreSQL results were impressive. They came in 11 seconds less than MySQL and MariaDB. That’s much faster. Conclusion All of the databases compared in this article require about the same effort to install and connect. But PostgreSQL clearly came out ahead when it came to the time required to add data to the database. Why? It’s hard to say definitively based on the information I collected in this basic test. But one possible explanation is that PostgreSQL uses heap tables rather than clustered indexes. This may improve performance. PostgreSQL’s multiversion concurrency control could also contribute to the performance bump. I only performed a basic test, of course. You could run many more benchmarks. Plus, when choosing which database to use with Docker, there are other factors to consider besides just performance, like how well the database works with the apps that will connect to it. Nonetheless, since few people have collected any sort of benchmarking data for containerized databases, the information above is a good starting point if you’re trying to decide which relational database to implement as part of your container infrastructure. Brena Monteiro is a software engineer with experience in the analysis and development of systems. She is a free software enthusiast and an apprentice of new technologies.