Comments - Getting Started with MariaDB Galera Cluster

Hi, I have a question around auto_increment values - is it always guaranteed to be in the ascending order? To give an example, say we have a 2 node cluster with the following settings

Node1: @@auto_increment_increment=2, @@auto_increment_offset=1 Node2: @@auto_increment_increment=2, @@auto_increment_offset=2

If 2 rows are inserted from Node1 into a table with an auto_increment primary key the IDs generated will be 1 and 3. If the next insert into the table is from Node2 the ID should be 4 as opposed to 2.

Thanks Raghav

Yes.

There is rarely a good reason not to have 3 nodes. With two you don't have a automated failure recovery

The autoincrement is sorted with the wsrep_auto_increment_control=1 (the default)

If the insert on Node 2 occurs before the from Node 1 applies you may get 2.

autoincrements can have gaps (due to transaction rollback). Use last_insert_id if you want the value of a last insert. Don't try to predict them.

Thanks Daniel, I used the two node example just to keep it simple.What happens if there are simultaneous inserts in more than one node for a particular table is that arbitrated somehow by the cluster and Ids generated accordingly?

Thanks

Raghav