What is a "topology" change?
Within an Indexima cluster, hyperindexes structures are uniformly spread on multiple nodes.
You may decide to remove one or more nodes because of a maintenance operation for example.
In that case, the remaining nodes of your cluster will split the data that was previously handled by the removed nodes.
That is what we call a "topology" change.
What happens when a "topology" change occurs?
For "READ" operations, this event is transparent.
When you are doing a more impacting operation like adding an index on a table, the following error message will be displayed:
Due to an elasticity event, you must do an INSERT/COMMIT (optionally empty) on table=YOUR_TABLE before adding a new index
You will have to send a COMMIT on that table before adding your index.
If you have many tables, you will have to send a COMMIT to each table.
To avoid sending COMMIT to each table, you can use this operation:
APPLY TOPOLOGY [IN schema_name];
- returns the list of tables that requires to be committed
- automatically send a COMMIT to each table listed above
You can also decide to use this operation on a specific schema
You can set the following variable in galactica.conf:
topology.change.autocommit = true
The default value of this variable is false.
when the variable is set to true, and a user is adding an index, and Indexima detects a COMMIT that needs to be sent on a table.
- The COMMIT will be automatically sent for this table.
- the addition of the index is put on hold waiting