By default, a PolarDB for MySQL cluster contains a primary node and a read-only row store node. When you add a read-only node, you can choose to add a read-only row store node or a read-only column store node. This topic describes how to add a read-only column store node.
Precautions
The In-Memory Column Index (IMCI) feature can be used together with the Voting Disk Service (VDS) module of the failover with hot replica feature only under these conditions:
For a cluster whose revision version is 8.0.1.1.42 and later or 8.0.2.2.23 and later:
If a cluster contains a read-only node where the failover with hot replica feature is enabled, you can add read-only column store nodes to the cluster.
If a read-only column store node already exists in a cluster, you cannot enable the hot standby feature for any read-only node in the cluster.
For a cluster whose revision version is earlier than 8.0.1.1.42 or earlier than 8.0.2.2.23, the IMCI feature cannot be used together with failover with hot replica feature.
If a cluster contains a read-only node for which the failover with hot replica feature is enabled, you cannot add read-only column store nodes to the cluster.
NoteIf you want to add a read-only column store node to the cluster, contact the technical support to disable VDS. When VDS is being disabled, all nodes in the cluster are automatically restarted.
If a read-only column store node already exists in a cluster, you cannot enable the hot standby feature for any read-only node in the cluster.
Prerequisites
Your cluster meets one of the following requirements:
A cluster of PolarDB for MySQL 8.0.1 whose revision version is 8.0.1.1.22 or later.
A cluster of PolarDB for MySQL 8.0.2 whose revision version is 8.0.2.2.12 or later.
Procedure
Log on to the PolarDB console.
In the upper-left corner, select the region where the cluster to which you want to connect is deployed.
Access the Add/Remove Node wizard by using one of the following methods:
Access the Add/Remove Node wizard from the Clusters page.
Find the cluster that you want to manage and click Add/Remove Node in the Actions column.
Access the Add/Remove Node wizard from the Basic Information page of the cluster.
Find the cluster that you want to manage and click the cluster ID to go to the Basic Information page.
In the Database Nodes section, click Add/Remove Node.
Select Add Read-only IMCI Node and click OK.
Click +Add an IMCI Node and select the node specifications from the drop-down list.
Set Switching Time as required. Select Terms of Service and click Buy Now.
Return to the Clusters page, and you can see the status of the cluster is Adding Node.
Results
After you make the payment, you are redirected to the Basic Information page of the cluster. After a while, the read-only column store node is added.
In the preceding figure, Read-only Columnar Node is the new column store node, and Read-only Node is the original row store node.