Error
Error Code:
1852
MariaDB Error 1852: Unique Index IGNORE Algorithm
Description
This error indicates that you are attempting to create a unique index using the `IGNORE` clause on an existing table. MariaDB requires the `COPY` algorithm for this operation to correctly identify and remove duplicate rows that would violate the unique constraint, which `INPLACE` or `INSTANT` algorithms cannot achieve. The error arises when a non-`COPY` algorithm is implicitly or explicitly used.
Error Message
Creating unique indexes with IGNORE requires COPY algorithm to remove duplicate rows
Known Causes
3 known causesDefault Incompatible Algorithm
MariaDB's default algorithm for `ALTER TABLE` operations may not be `COPY` when `IGNORE` is used with unique index creation, leading to this conflict.
Explicit Incompatible Algorithm
You have explicitly specified an `ALTER TABLE` algorithm (e.g., `INPLACE` or `INSTANT`) that cannot remove duplicate rows, making it incompatible with `IGNORE` for unique indexes.
Misunderstanding of IGNORE Clause
The `IGNORE` clause with unique indexes specifically requires the `COPY` algorithm to process and remove duplicate rows effectively from the table, a detail sometimes overlooked.
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