MySQL Connector/C Changelog

What's new in MySQL Connector/C 6.1.5

• Functionality Added or Changed:
• The server can now report session-state changes to client programs. Reportable session state consists of these values:
• The default schema (database)
• Session-specific values for system variables
• User-defined variables
• Temporary tables
• Prepared statements
• The MySQL client/server protocol now includes tracker information so that session state changes can be detected. One use for the tracker mechanism is that it provides a means for MySQL Connectors, Fabric, and client applications to determine whether any session context is available to ensure session migration from one server to another. (To change connections in a load-balanced environment, it is necessary to detect whether there is session state to take into consideration when deciding whether a switch can be made.)
• The user interface to control the tracker and retrieve state-change information from it has the following components, which enable implementation of state-change tracking on the client side:
• Clients can request notification when there is a change to any of the session state-related values just listed, in the form of a flag that is set in the OK packet received from the server after the change occurs. To control notification, enable or disable the session_track_state_change system variable. This variable is disabled by default.
• Clients can request notification of changed values for certain specific types of session state information:
• The default schema name. To control notification, enable or disable the session_track_schema system variable. This variable is enabled by default.
• The session values of system variables. Notification occurs for the system variables named by the session_track_system_variables system variable. By default, notification is enabled for time_zone, autocommit, character_set_client, character_set_results, and character_set_connection. (The latter three variables are those affected by SET NAMES.)
• To enable applications to extract the state-change information returned by the server, the MySQL C API includes a pair of functions:
• mysql_session_track_get_first() fetches the first state-change information received from the server.
• mysql_session_track_get_next() fetches any remaining state-change information received from the server. Following a successful call to mysql_session_track_get_first(), call this function repeatedly as long as it returns success.
• The mysqltest program has enable_session_track_info and disable_session_track_info commands to enable and disable tracking of session state-change information.
• Because there are new API functions (mysql_session_track_get_first(), mysql_session_track_get_next()), the client library ABI version is now 18.3. Shared library names now include 18.3 where appropriate.
• Bugs Fixed:
• Calling mysql_get_server_version() with an invalid connection handler argument caused the client to exit. Now it returns 0 and reports a CR_COMMANDS_OUT_OF_SYNC error. (Bug #18053212)
• The C client library could leak memory when client plugins were used. (Bug #17933308)
• On Windows, calling mysql_thread_init() call without mysql_init() caused the client to exit. Now it returns a nonzero result because it is an error to call mysql_thread_init() before the client library is initialized with mysql_library_init(). (Bug #17514920)
• There was a difference in certificate handling by yaSSL and OpenSSL (used for Community and Enterprise, respectively). OpenSSL expected a blank certificate to be sent when not all of the --ssl-ca, --ssl-cert, and --ssl-key options were specified, and yaSSL did not do so. To resolve this, yaSSL has been modified to send a blank certificate when an option is missing. (Bug #68788, Bug #16715064)