After having added a decent amount of entities to my Home Assistant setup, the user interface—especially the history tab, but also the history for each entity—became very sluggish. Having to wait for up to 30 seconds to see the history graph for a single entity became the norm with an sqlite file weighing in at 6GB and millions of entries in the “events” and “states” tables.
I wanted to keep my acquired data, so I had to migrate it from the current sqlite file to a MySQL database instead of starting anew. I’ve done this using Home Assistant version 0.81 and MariaDB 10. Some parts might change in the future.