MySQL 5.7 Release Notes - Download - MySQL

MySQL 5.7 Release Notes• When a connection is returned to the thread pool plugin, the connection thread contextmust be cleaned up. Previously, this was done using COM_CHANGE_USER (which is like themysql_change_user() C API function). However, that operation reauthenticates, which isunnecessary network roundtrip overhead in this context.Now it is possible for client connection state to be reset in a more lightweight manner without causingreauthentication. The API is exposed publicly through these changes:• A new COM_RESET_CONNECTION protocol command (defined in mysql_com.h)• A new mysql_reset_connection() C API function• A new resetconnection command for the mysql clientResetting a connection has effects similar to mysql_change_user() or an auto-reconnectexcept that the connection is not closed and reopened, and reauthentication is not done. Seemysql_change_user()) and see Controlling Automatic Reconnection Behavior).For more information, see mysql_reset_connection() and mysql — The MySQL Command-Line Tool.• A new mysql_get_option() C API function is available that returns the current value of applicablemysql_options() options. See mysql_get_option().• Because there are new API functions (mysql_get_option(), mysql_reset_connection()),the library ABI version is now 18.2. Shared library names now include 18.2 where appropriate.Bugs Fixed• Incompatible Change: For logging to the general_log and slow_log tables in the mysqldatabase, log lines containing multiple character sets were not always handled correctly. Thegeneral_log.argument and slow_log.sql_text columns now have been changed fromMEDIUMTEXT to MEDIUMBLOB. Consequently, no character set transformation is done for logging totables now, which aligns it with logging to files.If you upgrade to this release of MySQL from an earlier version, you must run mysql_upgrade (andrestart the server) to incorporate these changes into the mysql database. (Bug #14575847)• Important Change; Replication: START SLAVE UNTIL SQL_AFTER_GTIDS did not cause theslave to stop until the next GTID event was received following execution of the transaction having theindicated GTID, which could cause issues in the case when the next GTID event is delayed, or doesnot exist. Now the slave stops after completing the transaction with that GTID. (Bug #14767986)• Important Change; Replication: It was possible to start the server with binary logging enabled butno server ID specified; in such cases, the server would set server_id to 1 (rather than 0) whileslaves remained unable to connect.Now --server-id must be used when starting the server with binary logging enabled, otherwisethe server is unable to start. If --server-id=0 is used, this value is no longer changed by theserver; in this case, updates are written to the binary log, but slaves are unable to connect. Using--server-id without specifying a value has the same effect as setting it explicitly to 0. (Bug#11763963, Bug #56739)• InnoDB; Replication: The InnoDB mecached plugin would update a record before inserting tothe binlog, which would cause slave server replication to stop. The insert should occur before theupdate. (Bug #17358875)• InnoDB: When new indexes are added by an ALTER TABLE operation, instead of only savingtable-level statistics and statistics for the new indexes, InnoDB would save statistics for the entiretable, including the table's other indexes. This behavior slowed ALTER TABLE performance. (Bug#17848838, Bug #16511145)45