This topic describes the limits of ApsaraDB for ClickHouse.
Limits on purchasing and configuring clusters
Description | Limit |
Maximum number of clusters that can be purchased within each Alibaba Cloud account | 30 |
Maximum number of node groups that can be purchased for each cluster | 24 |
Maximum number of database accounts that can be created in each cluster | 500 |
Maximum number of scale-in, scale-out, upgrade, and downgrade operations on each cluster per day | 12 |
Maximum number of databases that can be created in each cluster | 256 |
Limits on specifications
For clusters of ApsaraDB for ClickHouse Community-compatible Edition, the memory in cluster specifications includes the memory that is occupied by the underlying operating system and related management services. Therefore, the available memory for compute nodes and ZooKeeper nodes of clusters may be less than the memory capacity that is supported by the cluster specifications.
Resource name | Memory occupied by the underlying operating system | Memory occupied by related management services |
Compute node | About 800 MB to 13 GB of memory is used. Higher specifications result in higher memory usage. | About 500 MB of memory is used. |
Zookeeper | About 800 MB to 2.5 GB of memory is used. Higher specifications result in higher memory usage. | About 500 MB of memory is used. |
Limits on features
A high-availability cluster of ApsaraDB for ClickHouse must use replicated tables.
By default, all ApsaraDB for ClickHouse nodes form a cluster named default. To execute a DDL statement on all nodes, add the
ON CLUSTER defaultkeyword phrase to the statement.You cannot configure remote_servers.
The File and URL table engines are not supported.
The File and URL table functions are not supported.
You cannot customize profiles.
Limits on 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 use the word system as the database name because system is reserved as the name of the 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 underscore (_). | A table name cannot contain single quotation marks ('), double quotation marks (''), exclamation points (!), or spaces. A table name cannot be an SQL reserved word. |
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 underscore (_). | A column name cannot contain single quotation marks ('), double quotation marks (''), exclamation points (!), or spaces. A column name cannot be an SQL reserved word. |
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. | - |
Password | A password must be 8 to 32 characters in length and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters include ! @ # $ % ^ & * ( ) _ + - =. | - |