MySQL took 21 years to fix this bug

MySQL bug #11472, filed in 2005, was finally fixed in 2026 after 21 years. The bug caused triggers not to fire when a foreign key cascade deleted rows. The root cause was an architectural decision from the late 1990s: MySQL implemented foreign keys inside the InnoDB storage engine rather than in the SQL layer, meaning cascade operations happened entirely within InnoDB without notifying the SQL layer where triggers live. The fix required moving foreign key logic out of InnoDB and up into the SQL layer — the major architectural work the team had been deferring for two decades.