Mysql：Changes in MySQL 5.7.9 (2015-10-21, General Availability)：很重要的版本！

Posted 2021-03-03 数据库探索

Changes in mysql 5.7.9 (2015-10-21, General Availability)

Server Administration

• A new SHUTDOWN SQL statement is available. This provides an SQL-level interface to the same functionality previously available using the mysqladmin shutdown command or the mysql_shutdown() C API function. See SHUTDOWN Statement.

  The mysql_shutdown() function and corresponding COM_SHUTDOWN client/server protocol command are deprecated and will be removed in a future MySQL version. Instead, use mysql_query() to execute a SHUTDOWN statement.

Functionality Added or Changed

• Incompatible Change; InnoDB: To better manage redo log format changes, the redo log header of the first redo log file (ib_logfile0) now includes a format version identifier and a text string that identifies the MySQL version that created the redo log files.

  A new boolean configuration option, innodb_log_checksums, replaces the innodb_log_checksum_algorithm option. innodb_log_checksums=ON enables a CRC-32C checksum, making it the only supported checksum for redo log pages.

  This patch also removes unused fields from the redo log header and checkpoint pages.

  Due to redo log format changes introduced by this patch, upgrading to or downgrading from MySQL 5.7.9 and higher requires a clean shutdown and, in some cases, removal of existing redo log files. For instructions related to this change, see Changes in MySQL 5.7, and Downgrade Notes. (Bug #21759424, Bug #78275, Bug #21752674)

   

• Important Change; InnoDB: DYNAMIC replaces COMPACT as the implicit default row format for InnoDB tables. A new configuration option, innodb_default_row_format, specifies the default InnoDB row format. Permitted values include DYNAMIC (the default), COMPACT, and REDUNDANT.

  The COMPACT row format remained the default row format until this release to ensure compatibility with older versions of InnoDB in MySQL 5.1 and earlier. Now that MySQL 5.1 has reached the end of its product lifecycle, the newer DYNAMIC row format becomes the default. For information about advantages of the DYNAMIC row format, see DYNAMIC Row Format.

  Newly created tables use the row format defined by innodb_default_row_format when a ROW_FORMAT option is not specified explicitly or when ROW_FORMAT=DEFAULT is used.

  Existing tables retain their current row format if a ROW_FORMAT option was specified explicitly. If a ROW_FORMAT option was not specified explicitly or if ROW_FORMAT=DEFAULT was used, any operation that rebuilds a table also silently changes the row format of the table to the format defined by innodb_default_row_format. For more information, see Defining the Row Format of a Table.

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