3354
MySQLERRORNotableDDL / IndexesHIGH confidence
Functional index cannot be created on a LOB (BLOB/TEXT) column
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 ((blob_col));
expected output
ERROR 3354 (HY000): Cannot create functional index on a LOB column.
Fix
Use a scalar function
Use a scalar function
CREATE INDEX idx ON t ((MD5(blob_col)));
Why this works
MD5 returns a fixed-length VARCHAR that is fully indexable.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3354 ER_FUNCTIONAL_INDEX_ON_LOB
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