3355
MariaDBERRORNotableDDL / IndexesHIGH confidence
Function is not allowed in a functional index expression
Production Risk
Low — DDL fails; no index is created.
How to reproduce
trigger — this will error
trigger — this will error
CREATE INDEX idx ON t ((NOW()));
expected output
ERROR 3355 (HY000): Function or expression is not allowed for functional index.
Fix
Use a deterministic function
Use a deterministic function
CREATE INDEX idx ON t ((YEAR(created_at)));
Why this works
YEAR() is deterministic and produces a stable integer key.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3355 ER_FUNCTIONAL_INDEX_FUNCTION_IS_NOT_ALLOWED
Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev