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System limits

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

  • CelerData uses the MySQL protocol for communication. You can connect to the CelerData 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 clusters, databases, tables, views, columns, partitions, usernames, and roles:

    • The names 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. The column name, table name, and database name cannot exceed 1023 characters in length.
    • Except for column names, other names must start with a lowercase or uppercase letter.
    • Column names can start with an underscore (_).
    • Database, table, and view names are case-sensitive. Column names are not case-sensitive.

  • Password requirements for members:

    • The password can contain uppercase letters (A-Z), lowercase letters (a-z), and digits (0-9).
    • The password must contain at least eight characters, including at least one letter and at least one digit.
    • The password cannot contain four identical or consecutive letters or digits like 11111, 12345, abcde, or qwert.

  • 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 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.

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

  • CelerData does not support modifying column names in tables.

  • By default, a query can be nested with a maximum of 10,000 subqueries.