Restoring or Exporting Data for Downgrade in MariaDB

2. Data Export and Import: This is a riskier option, but it might work for minor version downgrades. Here's the process:

   • Use mysqldump on the new MariaDB version to export your data as a SQL file. This creates a file containing all the SQL statements needed to recreate your database structure and data.
   • Install the older version of MariaDB.
   • Use mysql on the older version to import the SQL file you created earlier. This attempts to import the data structure and contents from the newer version into the older MariaDB.

Important points to consider:

• Downgrading with the export/import method might not work perfectly, especially for major version jumps. Newer versions may introduce features or data structures that the older version doesn't understand. This could lead to errors or data loss.
• It's always recommended to thoroughly test your data after any downgrade attempt.

mysqldump -u username -p database_name > database_backup.sql

Replace the following:

• username: Your MariaDB username with access to the database.
• password: The password for your MariaDB user (enter when prompted).
• database_name: The name of the database you want to export.

This command will dump the structure and data of database_name into a file named database_backup.sql.

mysql -u username -p database_name < database_backup.sql

• database_name: The name of the database you want to import into (should be the same as the exported one).

This command will try to import the data and structure from database_backup.sql into the specified database on the older MariaDB server.

1. Replication with Fallback:

   • This approach involves setting up replication between your new MariaDB server and an older server with the desired version.
   • Replication allows the new server to keep the older server updated with changes in real-time (or with a slight delay).
   • If encountering issues with the new version, you can stop replication on the new server and promote the older server as the primary, essentially "falling back" to the previous version.

2. Partial Backups and Tools:

   • This approach is more complex and requires specialized tools like xtrabackup (for InnoDB tables).
   • xtrabackup allows for creating "hot backups" of specific tablespaces or databases while the MariaDB server is running.
   • In theory, these backups could potentially be restored on an older MariaDB server with compatible table formats, but success depends heavily on the specific versions involved and potential schema changes.

Things to Consider:

• Both these approaches require additional setup and configuration compared to the basic export/import method.
• Replication introduces complexity and potential overhead to your system.
• Restoring partial backups with tools like xtrabackup might not be straightforward and requires a good understanding of the tool and potential compatibility issues.

Recommendation:

• For most situations, a full backup restore is the safest and most reliable option.
• If you don't have a full backup, then the export/import method might be a gamble, but proceed with caution and thorough testing.
• Consider the complexity of your situation and technical expertise before attempting replication or partial backup restoration for downgrading.