System limits
This topic describes the rules and limits that apply when you use StarRocks.
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StarRocks uses the MySQL protocol for communication. You can connect to the StarRocks cluster via a MySQL client or JDBC. We recommend that you use a MySQL client whose version is 5.1 or later. Versions earlier than 5.1 do not support usernames that are longer than 16 characters.
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Naming conventions for objects such as catalogs, databases, tables, views, partitions, columns, indexes, usernames, roles, repositories, resources, storage volumes, and pipes:
- The name can only consist of digits (0-9), letters (a-z or A-Z), and underscores (_). Usernames can be all digits.
- The name can start with a letter or an underscore (_).
- The name cannot exceed 64 characters in length, among which:
- Database name cannot exceed 256 characters.
- Table name and column name cannot exceed 1024 characters.
- Username cannot exceed 128 characters.
- Column name (column alias), partition name, and index name are not case-sensitive. Other names are case-sensitive.
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Naming conventions for labels: You can specify the label of a job when you load data. The label name can consist of digits (0-9), letters (a-z or A-Z), and underscores (_), and cannot exceed 128 characters in length. Label names can start with a letter or an underscore (_).
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When you create a table, the key column cannot be of the FLOAT or DOUBLE type. You can use the DECIMAL type to represent decimals.
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The maximum length of a VARCHAR value varies in different versions:
- In versions earlier than StarRocks 2.1, the length ranges from 1 to 65533 bytes.
- [Preview] In StarRocks 2.1 and later versions, the length ranges from 1 to 1048576 bytes. Maximum length of a VARCHAR value = Maximum row size (1048578 bytes) - Length prefix (2 bytes). The length prefix indicates the number of bytes in the value.
- The default length is 1 byte.
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StarRocks supports only UTF-8 encoding, not GBK.
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StarRocks does not support modifying column names in tables.
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StarRocks does not support modifying the table types of an existing table. For example, you cannot change a Duplicate Key table to a Primary Key table. You must create a new table.
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By default, a query can be nested with a maximum of 10,000 subqueries, which is controlled by the FE parameter
expr_children_limit
.