Error
Error Code:
1823
MariaDB Error 1823: Foreign Key System Table Failure
Description
Error 1823 indicates that MariaDB failed to record a foreign key constraint in its internal system tables. This typically occurs during `ALTER TABLE` or `CREATE TABLE` operations when adding foreign key relationships, signaling an underlying issue preventing the constraint from being properly established and tracked by the database system.
Error Message
Failed to add the foreign key constraint '%s' to system tables
Known Causes
4 known causesData Type or Collation Mismatch
The data types, lengths, or collations of the foreign key column(s) do not exactly match those of the referenced primary or unique key column(s).
Existing Referential Integrity Violation
The child table contains existing data that violates the foreign key constraint, such as rows referencing non-existent parent keys, preventing the constraint from being enforced.
Insufficient User Privileges
The database user attempting to add the foreign key constraint lacks the necessary `ALTER` or `REFERENCES` privileges on the involved tables.
Underlying Table or Server Issue
Less common, but corruption in the table definition or temporary server resource issues could prevent the system tables from being updated.
Solutions
3 solutions available1. Verify and Repair System Tables medium
Checks for corruption in system tables and attempts to repair them.
1
Connect to your MariaDB server using the `mysql` client or a GUI tool.
2
Execute a command to check the integrity of system tables. For InnoDB, this often involves checking the `mysql.innodb_table_stats` and `mysql.innodb_index_stats` tables. For other system tables, `mysqlcheck` is more general.
sudo mysqlcheck -c --all-databases -u root -p3
If `mysqlcheck` reports any errors, attempt to repair the corrupted tables.
sudo mysqlcheck -r --all-databases -u root -p4
Restart the MariaDB server to ensure all changes are applied.
sudo systemctl restart mariadb5
Attempt to add the foreign key constraint again.
ALTER TABLE your_table ADD CONSTRAINT fk_name FOREIGN KEY (column_name) REFERENCES parent_table(parent_column_name);2. Temporarily Disable Foreign Key Checks easy
Disables foreign key checks to allow schema modifications, then re-enables them.
1
Connect to your MariaDB server.
2
Temporarily disable foreign key checks for the current session.
SET foreign_key_checks = 0;3
Attempt to add the foreign key constraint.
ALTER TABLE your_table ADD CONSTRAINT fk_name FOREIGN KEY (column_name) REFERENCES parent_table(parent_column_name);4
Re-enable foreign key checks.
SET foreign_key_checks = 1;5
Verify that the foreign key constraint has been successfully added by querying the information schema.
SELECT * FROM information_schema.KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_NAME IS NOT NULL AND TABLE_NAME = 'your_table';3. Check and Correct System Table Permissions medium
Ensures the MariaDB user has sufficient privileges to modify system tables.
1
Connect to your MariaDB server as a user with administrative privileges (e.g., `root`).
2
Grant necessary privileges for modifying system tables. This is a broad grant and should be used with caution. A more targeted approach might be needed based on the specific system table involved.
GRANT ALL PRIVILEGES ON mysql.* TO 'your_user'@'localhost';
FLUSH PRIVILEGES;3
If you are using a specific user for schema modifications, ensure they have these privileges.
4
Attempt to add the foreign key constraint again.
ALTER TABLE your_table ADD CONSTRAINT fk_name FOREIGN KEY (column_name) REFERENCES parent_table(parent_column_name);