ae1d17f52d
Starting with commit 210855ce5d6803f41d672d75be3334726f52a9df Valgrind became aware that the unused tail of the buffer that is returned by thd_get_xid() is actually uninitialized. The problem should exist already in MySQL 5.0. I was able to repeat it on MariaDB Server 5.5 with some additional instrumentation. InnoDB is allocating 128+4+4 bytes for the XID and the lengths of its components, even when the XID is shorter than 64+64 bytes. In MariaDB Server 10.3, while running the test main.xa_binlog, in the xid_t::set() that is called by sql_yacc.yy, the 128-byte data buffer was uninitialized according to Valgrind, and only the first bytes were initialized. When the xid_t::data was copied to thd.transaction.xid_state.xid.data, it happened so that the entire target buffer was considered initialized. With MariaDB Server 10.4 since the said commit, Valgrind will correctly be detect the tail of the buffer as uninitialized. The impact of this bug is as follows: (1) InnoDB will write unnecessarily much redo log for XA PREPARE. (2) InnoDB will write garbage bytes to the redo log and undo log pages. (3) The garbage should be 'harmless', because on recovery, only the actual payload of the XID will be used, based on the written length. trx_rseg_write_wsrep_checkpoint(), trx_undo_write_xid(): Write only the actually used length of xid->data to the data page, and zero out the rest of the buffer by mlog_memset().
Code status:
travis-ci.org (10.4 branch)ci.appveyor.com
MariaDB: drop-in replacement for MySQL
MariaDB is designed as a drop-in replacement of MySQL(R) with more features, new storage engines, fewer bugs, and better performance.
MariaDB is brought to you by the MariaDB Foundation and the MariaDB corporation. Please read the CREDITS file for details about the MariaDB Foundation, and who is developing MariaDB.
MariaDB is developed by many of the original developers of MySQL who now work for the MariaDB Corporation, the MariaDB Foundation and by many people in the community.
MySQL, which is the base of MariaDB, is a product and trademark of Oracle Corporation, Inc. For a list of developers and other contributors, see the Credits appendix. You can also run 'SHOW authors' to get a list of active contributors.
A description of the MariaDB project and a manual can be found at:
https://mariadb.com/kb/en/mariadb-vs-mysql-features/
https://mariadb.com/kb/en/mariadb-versus-mysql-compatibility/
https://mariadb.com/kb/en/library/new-and-old-releases/
As MariaDB is a full replacement of MySQL, the MySQL manual at http://dev.mysql.com/doc is generally applicable.
Help
More help is available from the Maria Discuss mailing list https://launchpad.net/~maria-discuss and the #maria IRC channel on Freenode.
Live QA for beginner contributors
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New contributors can ask questions any time, but we will provide immediate feedback during that interval.
Licensing
NOTE:
MariaDB is specifically available only under version 2 of the GNU General Public License (GPLv2). (I.e. Without the "any later version" clause.) This is inherited from MySQL. Please see the README file in the MySQL distribution for more information.
License information can be found in the COPYING file. Third party license information can be found in the THIRDPARTY file.
Bug Reports
Bug and/or error reports regarding MariaDB should be submitted at: https://jira.mariadb.org
For reporting security vulnerabilities see: https://mariadb.org/about/security-policy/
Bugs in the MySQL code can also be submitted at: https://bugs.mysql.com
The code for MariaDB, including all revision history, can be found at: https://github.com/MariaDB/server