Why we're ending support for MySQL in 12.1

What this post added

GitLab is ending support for MySQL in version 12.1. This decision was made due to MySQL's limitations for GitLab's specific use cases, including performance issues with nested groups, limitations on column sizes, lack of support for TEXT type columns without length specification, and absence of partial indexes. These limitations also impacted features like Geo. Supporting MySQL required complex, backend-specific code, increasing merge request complexity and slowing down development velocity. CI systems also ran test suites twice, increasing costs. By removing MySQL support, GitLab can leverage backend-specific capabilities like PostgreSQL's LATERAL JOIN. Usage Ping data indicated a strong customer preference for PostgreSQL, with a significant majority of instances already migrated. The post provides migration documentation for users still on MySQL.