A common migration path from standalone MySQL/Percona Server to a Percona XtraDB Cluster (PXC) environment involves some measure of time where one node in the new cluster has been configured as a slave of the production master that the cluster is slated to replace. In this way, the new cluster acts as a slave of the production environment – traditional replication takes care of getting the data into the cluster, and then Galera replication handles the intra-cluster traffic. This often works without issue, although there is one case that I’ve encountered recently where special care must be taken to properly configure the stream to ensure that replication does not break. If you use multi-valued inserts with auto-increment columns, then this post is for you.

For purposes of our discussion, assume that we have a basic 3-node PXC cluster that we’ve set up …

The title is SEO bait – you can’t do it. We’ve seen a few recurring patterns trying to achieve similar – and I thought I would share with you my favorite two:

Option #1: Use a table to insert into, and grab the insert_id:

CREATE TABLE option1 (id int not null primary key auto_increment) engine=innodb;

# each insert does one operations to get the value:
INSERT INTO option1 VALUES (NULL);
# $connection->insert_id();

Option #2: Use a table with one just row:

CREATE TABLE option2 (id int not null primary key) engine=innodb;
INSERT INTO option2 VALUES (1); # start from 1

# each insert does two operations to get the value:
UPDATE option2 SET id=@id:=id+1;
SELECT @id;

So which is better? I don’t think it’s that easy to tell at a first glance, since option 2 does look more elegant – but if the next value is fetched as part of a transaction – I can see a potential …

In two words: online operations. In a paragraph: Forget partitioning, row-based replication and events. The big reasons most people are going to salivate over 5.1, and probably start plans to upgrade now, are the online operations:

• online ALTER TABLE for column rename, column default value change, and adding values to the end of an ENUM/SET
• Online, table-based logging. No more need to restart your server to enable or change the general or slow query logs. You can have the standard file-based output or choose a table format…which you can query.

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