Error
Error Code:
1170
MySQL Error 1170: BLOB/TEXT Key Length Missing
Description
This error occurs when you attempt to create an index on a BLOB or TEXT column in MySQL without specifying a prefix length. MySQL requires a specific length for indexes on these large data types to optimize storage and lookup efficiency. Without it, the database cannot properly manage the index.
Error Message
BLOB/TEXT column '%s' used in key specification without a key length
Known Causes
3 known causesAttempting Direct Index on BLOB/TEXT
This happens when you try to create an index directly on a BLOB or TEXT column using `CREATE INDEX` or `ALTER TABLE` without specifying a length.
Missing Prefix Length in Table Definition
When defining a table with a BLOB or TEXT column, you might declare an index on it within the `CREATE TABLE` statement but forget to include the required prefix length.
ORM/Framework Generating Invalid DDL
Object-Relational Mapping (ORM) tools or database migration frameworks might generate DDL that incorrectly omits the prefix length when indexing BLOB/TEXT columns.
Solutions
Coming SoonDetailed step-by-step solutions for this error are being prepared. In the meantime, try these general troubleshooting tips:
General Troubleshooting Tips
- Check the error message carefully for specific details
- Review recent changes that might have caused the error
- Search for the exact error code in the official documentation
- Check log files for additional context
- Try restarting the application or service