PolarDB:Add a columnstore read-only instance

Background information

PolarDB-X uses a read/write splitting architecture for its columnstore index. Columnar nodes handle columnstore writes, while CN nodes handle columnstore reads. A columnstore read-only instance refers specifically to columnstore access. By deploying additional CN nodes, you can achieve physical isolation for columnstore query paths and implement a read-only instance.

Notes

• A columnstore read-only instance must be in the same region as its primary instance but can be in a different zone.

• A columnstore read-only instance cannot exist independently and must belong to a primary instance. If you create a database on the primary instance, it is automatically replicated to the read-only instance. Similarly, if you delete a database from the primary instance, the corresponding database is also deleted from the read-only instance.

• A columnstore read-only instance can access only tables that have a columnstore index. Queries on tables without a columnstore index will return an error.

Procedure

1. Log on to the PolarDB distributed console.

2. In the upper-left corner of the page, select the region where the target instance resides.

3. On the Instances page, click the PolarDB-X 2.0 tab.

4. Find the target instance and click Columnstore Read-only Instance in the Actions column. Alternatively, click the instance to go to its details page, then in the Columnstore Read-only Instance section on the right, click Add Columnstore Read-only Instance.

5. In the dialog box that appears, configure the following parameters.

   Parameter	Description
   Product Type	Select subscription or pay-as-you-go. Note Subscription is a prepaid billing method suitable for stable production environments and offers a lower unit price than pay-as-you-go. Pay-as-you-go is a postpaid billing method typically used for testing or learning purposes. To create a pay-as-you-go instance, ensure your Alibaba Cloud account balance is at least USD 100.
   Region	The read-only instance must be in the same region as the primary instance. For example, if the primary instance is in China (Hangzhou), the region for the read-only instance is automatically set to China (Hangzhou) and cannot be changed.
   Zone	Select a zone for the read-only instance. The primary instance and the read-only instance can be in different zones.
   Network type	Fixed as virtual private cloud (VPC) and cannot be changed.
   Virtual private cloud (VPC)	Select a VPC.
   vSwitch	Select a virtual switch.
   MySQL version	Fixed as 5.7 and cannot be changed.
   Instance selection model	Custom model. This setting cannot be changed.
   Specification series	Supports General-purpose columnstore and Dedicated columnstore specifications.
   Compute node specifications	Sold as node specifications × number of workers. Select a specification to set the number of CPU cores and memory size for the instance. Note A columnstore read-only instance includes only compute layer nodes and does not include row store storage layer nodes.
   Number of workers	Select the number of nodes for the selected specification. The default is 2 nodes.
   Storage class	Fixed as local SSD and cannot be changed.
   Storage fee	Columnstore compute nodes do not incur data storage fees. No capacity selection is required.
   Subscription duration	Select the subscription duration. Note This parameter is available only when the billing method is subscription.
   Quantity	Select the number of instances to purchase.

6. Accept the Service Agreement and click Buy Now.

7. On the Payment page, confirm the order and payment method, then click Pay.

8. After successful payment, wait 3–5 minutes for the service to be activated. Then, go to the Instances page in the console to view the newly created columnstore read-only instance.