MySQL 9.1 Release Notes
MySQL supports upgrading between minor versions (within an LTS series) and to the next major version (across an LTS series). Upgrading provides the latest features, performance, and security fixes.
To prepare and help ensure that your upgrade to the latest MySQL release is successful, we recommend the following best practices:
The MySQL Release Model makes a distinction between LTS (Long Term Support) and Innovation Releases. LTS releases have 8+ years of support and are meant for production use. Innovation Releases provide users with the latest features and capabilities. Learn more about the MySQL Release Model.
Performing a minor version upgrade is straightforward while major version upgrades require strategic planning and additional testing before the upgrade. This guide is especially useful for major version upgrades.
There are three main ways to upgrade MySQL, read the associated documentation to determine which type of upgrade is best suited for your situation.
An in-place upgrade: Replacing the MySQL Server packages.
A logical upgrade: exporting SQL from the old MySQL instance to the new.
A replication topology upgrade: account for each server's topology role.
If your current operating system is not supported by the new version of MySQL, then plan to upgrade the operating system as otherwise an in-place upgrade is not supported.
For a current list of supported platforms, see: https://www.mysql.com/support/supportedplatforms/database.html
Each major version comes with new features, changes in behavior, deprecations, and removals. It is important to understand the impact of each of these to existing applications.
MySQL Shell's Upgrade Checker Utility detects incompatibilities between database versions that must be addressed before performing the upgrade. The util.checkForServerUpgrade() function verifies that MySQL server instances are ready to upgrade. Connect to the existing MySQL server and select the MySQL Server version you plan to upgrade to for the utility to report issues to address prior to an upgrade. These include incompatibilities in data types, storage engines, and so on.
You are ready to upgrade when the upgrade checking utility no longer reports any issues.
After completing the upgrade checker's requirements, next test your applications on the new target MySQL server. Check for errors and warnings in the MySQL error log and application logs.
We recommend benchmarking your own applications and workloads by comparing how they perform using the previous and new versions of MySQL. Usually, newer MySQL versions add features and improve performance but there are cases where an upgrade might run slower for specific queries. Possible issues resulting in performance regressions:
Prior server configuration is not optimal for newer version
Changes to data types
Additional storage required by Multi-byte character set support
Storage engines changes
Dropped or changed indexes
Stronger encryption
Stronger authentication
SQL optimizer changes
Newer version of MySQL require additional memory
Physical or Virtual Hardware is slower - compute or storage
For related information and potential mitigation techniques, see Valid Performance Regressions.
To minimize risk, it is best keep the current system running while running the upgraded system in parallel.
Practice and do a run though prior to upgrading your production server. Thoroughly test the upgrade procedures before upgrading a production system.