Mysql：Changes in MySQL 5.7.13 (2016-06-02, General Availability)：maximum length of MySQL user names was increased from 16 to 32 characters

• The size of these mysql system table columns is increased:

  • The definer column of the event and proc tables

  • The grantor column of the procs_priv and tables_priv tables

  In each case, the column previously was defined as CHAR(77), where 77 was chosen to permit a user_name@host_name string containing a user name up to 16 characters, a @ character, and a host name up to 60 characters. Each column now is defined as CHAR(93), reflecting an increase in permitted user name length from 16 to 32 characters.

• A similar change from CHAR(77) to CHAR(93)applies to the DEFINER column of these INFORMATION_SCHEMA tables: EVENTS, ROUTINES, TRIGGERS, VIEWS. Along with the changes to INFORMATION_SCHEMA tables, output from any corresponding SHOW statements now displays DEFINER values up to 93 characters. Examples of affected statements: SHOW EVENTS, SHOW TRIGGERS, SHOW PROCEDURE STATUS.

If you upgrade to this MySQL release from an earlier version, you must run mysql_upgrade (and restart the server) to incorporate the changes to the mysql system database. A server from MySQL 5.7.13 or higher for which mysql_upgrade has not been run continues to permit a maximum of 77 characters in the system tables mentioned previously, and an ER_USER_COLUMN_OLD_LENGTH error will occur in those system table contexts where a user_name@host_name value from 78 to 93 characters long is given.

• It is possible to use ALTER TABLE to change the default value of a column col_name, which may change the value of a generated column expression that refers to the column using DEFAULT(col_name). For this reason, ALTER TABLE operations that change the definition of a column now cause a table rebuild if any generated column expression uses DEFAULT(). (Bug #80299, Bug #22680839)

It is possible to use ALTER TABLE to change the default value of a column col_name, which may change the value of a generated column expression that refers to the column using DEFAULT(col_name). For this reason, ALTER TABLE operations that change the definition of a column now cause a table rebuild if any generated column expression uses DEFAULT().

Mysql：Changes in MySQL 5.7.13 (2016-06-02, General Availability)：maximum length of MySQL user names was increased from 16 to 32 characters

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