Description:
Hi,
currently, the only way to get the GTID of the last transaction is by enabling session_track_gtids ([1]) and using the 2 following connector functions:
- mysql_session_track_get_first ([2])
- and mysql_session_track_get_next ([3]).
[1]: https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_session_track_...
[2]: https://dev.mysql.com/doc/refman/5.7/en/mysql-session-track-get-first.html
[3]: https://dev.mysql.com/doc/refman/5.7/en/mysql-session-track-get-next.html
Having the GTID in the OK packet is better than getting it from a session variable (Bug#84747) as it saves a round-trip to the server. However, to enable this performance gain, session_track_gtids needs to be enabled at the global level, which wastes resources when this information is not needed. Setting session_track_gtids at the session level is not very useful, as it needs a round-trip to the server, which would be the same as reading a session variable.
To remove this problem, would you please consider implementing a way to tell MySQL at the statement level that the GTID of the last transaction should be put in the OK packet ? Something like an optimizer hint would do. I could suggest the following:
- COMMIT /* session_track_gtids = OWN_GTID */;
- INSERT /* session_track_gtids = OWN_GTID */ ...;
- UPDATE ... DELETE ...
- ALTER TABLE /* session_track_gtids = OWN_GTID */ ...;
- ...
Note that a hint on COMMIT is not enough, one should be able to get the last GTID in auto-commit mode and for DDL.
Many thanks,
JFG
How to repeat:
This is a feature request.
Suggested fix:
Implement a way to tell MySQL, in a statement, that the GTID of the last transaction should be put in the OK packet.
