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Version: Stable-2.5

System limits

This topic describes the rules and limits that apply when you use StarRocks.

  • 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.

  • Naming conventions for catalogs, databases, tables, views, partitions, columns, usernames, and roles:

    • The name can only consist of digits (0-9), letters (a-z or A-Z), and underscores (_). Usernames can be all digits.
    • The name cannot exceed 64 characters in length, among which the catalog, database, table, and column names cannot exceed 1023 characters in length.
    • Catalog, database, table, view, partition, and roles names must start with a lowercase or uppercase letter.
    • Column names can start with an underscore (_).
    • Catalog, database, table, view, username, and role names are case-sensitive. Column and partition names are not case-sensitive.
  • Naming conventions for labels: You can specify the label of a job when you import data. The label name can consist of underscores (_), letters (a-z or A-Z), and digits (0-9), and cannot exceed 128 characters in length. The label name has no requirement for the starting character.

  • 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.

  • 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.
  • StarRocks supports only UTF-8 encoding, not GBK.

  • StarRocks does not support modifying column names in tables.

  • 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.

  • By default, a query can be nested with a maximum of 10,000 subqueries, which is controlled by the FE parameter expr_children_limit.