To ensure cluster stability and security, take note of the limits on the use of ApsaraDB for ClickHouse.

Feature limits

  • An ApsaraDB for ClickHouse cluster of the High-availability Edition must use a replicated table engine.
  • When you perform a data definition language (DDL) operation, you must add the ON CLUSTER default keyword phrase to the statement. This way, the DDL operation is performed on all the nodes of the cluster.
  • ApsaraDB for ClickHouse supports only distributed tables. Multiple ApsaraDB for ClickHouse nodes automatically form a distributed cluster. Non-replicated tables are not supported. By default, all ApsaraDB for ClickHouse nodes form a cluster named default. To perform a DDL operation, you must add the ON CLUSTER default keyword phrase to the statement to perform the DDL operation on all the nodes.
  • You cannot configure remote clusters.
  • File and URL table engines are not supported.
  • Table functions such as file and url are not supported.
  • You cannot define custom profiles.

Object naming conventions

Object Naming convention Limit
Database A database name can be up to 64 characters in length and can contain letters, digits, and underscores (_). It must start with a lowercase letter and cannot contain consecutive underscores (_). You cannot name a database system, which is the name of a built-in database.
Table A table name must be 1 to 127 characters in length and can contain letters, digits, and underscores (_). It must start with a letter or an underscore (_). A table name cannot contain single quotation marks ('), double quotation marks (''), exclamation points (!), or spaces. A table name cannot be an SQL reserved keyword.
Column A column name must be 1 to 127 characters in length and can contain letters, digits, and underscores (_). It must start with a letter or an underscore (_). A column name cannot contain single quotation marks ('), double quotation marks (''), exclamation points (!), or spaces. A column name cannot be an SQL reserved keyword.
Account An account name must be 2 to 16 characters in length and can contain lowercase letters, digits, and underscores (_). It must start with a lowercase letter and end with a lowercase letter or digit. N/A
Password A password must be 8 to 32 characters in length and must contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters include ! @ # $ % ^ & * ( ) _ + - = N/A

Limits on purchase and configurations

Limit Description Remarks
Maximum number of clusters that you can purchase within an Alibaba Cloud account 30 During public preview, you can purchase only up to five clusters within an Alibaba Cloud account.
Maximum number of node groups that you can purchase for each cluster 24 If you need more node groups, submit a ticket or call the customer service line to apply to extend the limit.
Maximum number of database accounts that you can create in each cluster 500 N/A
Maximum number of scale-out, scale-in, scale-up, and scale-down operations on each cluster per day 12 N/A
Maximum number of databases that you can create in each cluster 256 N/A