Splitting databases
Warning
This is still proof-of-concept level. Use with care.
In order to scale at some point it might make sense to split out some tables or apps which allow it as they might be better off with a different replication methods, etc.
A first attempt we do right now with the activity table. In order to make use of this, the app/table needs to match the following criteria:
No other apps are allowed to have queries directly to the table
No JOINs are performed between this table and any other tables not on this new separate connection
The app needs to support a connection parameter prefix
In case of the activity app the prefix is activity_
. If a database config is not
specified it falls back to the normal database configuration option for this value:
activity_dbuser
falling back todbuser
activity_dbpassword
falling back todbpassword
activity_dbname
falling back todbname
activity_dbhost
falling back todbhost
activity_dbport
falling back todbport
activity_dbdriveroptions
falling back todbdriveroptions
Note
It is not possible to use a different database type (SQLite, MySQL, PostrgreSQL, Oracle) for a split database. Also in case of MySQL and MariaDB the utf8mb4 option needs to be the same on both databases.
Initial splitting
For the initial split the affected tables have to be copied over to the new database, in case of the activity app these are:
oc_activity
oc_activity_mq
Enable maintenance mode
Make sure optional database changes are applied:
occ db:convert-mysql-charset
occ db:convert-filecache-bigint
occ db:add-missing-indices
occ db:add-missing-primary-keys
occ db:add-missing-primary-keys
3. Specify the desired configuration values 3. Copy the 2 tables to the new database 4. Disable maintenance mode
Migrations on updates
We will try to avoid migrations on those tables in the future, but it might be necessary at some point. We hope to have a dedicated plan by the time this happens. For now a potential way would be:
Enable maintenance mode
Update as usual
Execute manual queries for schema changes provided by the app authors
Execute manual queries for data changes provided by the app authors
Disable maintenance mode