In this section, we are going to be talking about updates, upgrades, and migrations. To define the terminology:
An update is a point release, for example, from TiDB 2.0.4 to 2.0.7. Updates are always expected to be safe to perform, and contain fixes to critical bugs (either security of functionality). They typically will not contain new functionality or changes to behaviors. I usually group Operating System patches into the same category, since it is important to keep up to date with vendor supported patches.
An upgrade could be from TiDB 1.0 to 2.0 or TiDB 2.0 to 2.1. These releases contain additional functionality, and while typically compatible it is recommended to apply basic testing to ensure everything works as expected for your specific workload.
A migration is converting from one technology to another. For example, migrating from MySQL to TiDB.
In this section, we will be describing all three as it applies to TiDB and the KOST stack. Starting with updates and upgrades.