Error
Error Code:
1808
MariaDB Error 1808: Table Schema Mismatch
Description
This error indicates that the definition of a table (its columns, data types, or constraints) does not match the schema expected by the server or a specific operation. It commonly arises when attempting to access, modify, or restore tables whose structure differs from the current database's understanding.
Error Message
Schema mismatch (%s
Known Causes
4 known causesIncompatible Database Restore
Restoring a database or table from a backup where the schema definition differs from the target server's expected structure.
Application-Database Schema Drift
The schema expected by an application or client connection does not align with the actual schema defined in the MariaDB server.
Manual DDL Inconsistencies
Direct Data Definition Language (DDL) operations have created a table schema that is internally inconsistent or incompatible with other database components.
Replication Schema Divergence
In a replication setup, the schema of a table on the replica server has diverged from the master server's expected schema.
Solutions
3 solutions available1. Rebuild Table with `ALTER TABLE` medium
Reconstruct the table to resolve schema inconsistencies.
1
Identify the table experiencing the schema mismatch. The error message usually provides context, or you can check your application logs.
2
Use `ALTER TABLE` with the `FORCE` option to rebuild the table. This forces MariaDB to rewrite the table with the current schema definition. It's crucial to back up your data before proceeding.
ALTER TABLE your_table_name FORCE;3
If `FORCE` doesn't resolve the issue, or if you suspect a more complex corruption, consider exporting and re-importing the table. First, export the table structure and data.
mysqldump -u your_user -p your_database your_table_name > your_table_name_backup.sql4
Then, drop the problematic table.
DROP TABLE your_table_name;5
Finally, re-import the table from the backup file.
mysql -u your_user -p your_database < your_table_name_backup.sql2. Check and Repair Table with `REPAIR TABLE` easy
Attempt to fix minor corruption or inconsistencies using MariaDB's repair utility.
1
Connect to your MariaDB server using a client (e.g., `mariadb` command-line client or a GUI tool).
2
Execute the `REPAIR TABLE` command for the affected table. This command attempts to fix corrupted table data or indexes.
REPAIR TABLE your_table_name;3
If the table uses the `MYISAM` storage engine, you might need to use `REPAIR TABLE your_table_name USE_FRM;` as a fallback. However, `InnoDB` is more common and generally self-healing.
REPAIR TABLE your_table_name USE_FRM;4
After repair, verify the table's integrity and data accuracy.
3. Verify Table Definition Against Data Files advanced
Manually inspect and reconcile differences between the table's defined schema and its underlying data files.
1
Locate the data directory for your MariaDB instance. This is typically defined by the `datadir` variable in your `my.cnf` or `my.ini` configuration file.
SHOW VARIABLES LIKE 'datadir';2
Navigate to the directory corresponding to your database and find the files for the problematic table (e.g., `your_table_name.frm`, `your_table_name.ibd` for InnoDB, or `your_table_name.MYD`, `your_table_name.MYI` for MyISAM).
3
Compare the schema definition obtained from `SHOW CREATE TABLE your_table_name;` with the contents or structure of the data files. This is a complex step and might require specialized tools or knowledge of the storage engine's file format.
SHOW CREATE TABLE your_table_name;4
If discrepancies are found (e.g., a column exists in the `.frm` file but not in the `.ibd` file, or vice-versa), this indicates severe corruption. A rebuild or re-import (as described in Solution 1) is usually the safest course of action.