d2fa5f8cfc
For a table column `a`, the above expressions logically equate to false in all cases. With this patch the optimizer knows about this and queries like: SELECT * FROM t1 WHERE a!=a no longer need to evaluate a!=a for every row. The same applies if the expression was `a<a`, or `a>a` An `EXPLAIN SELECT COOUNT(*) FROM t1 WHERE a<a` will show: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE Similarly `NOT (a!=a)` is always true. EXPLAIN SELECT COUNT(*) FROM t1 WHERE not (a!=a); id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
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
MariaDB has a dedicated time each week when we answer new contributor questions live on Zulip and IRC. From 8:00 to 10:00 UTC on Mondays, and 10:00 to 12:00 UTC on Thursdays, anyone can ask any questions they’d like, and a live developer will be available to assist.
New contributors can ask questions any time, but we will provide immediate feedback during that interval.
License
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, COPYING.LESSER, and COPYING.thirdparty files.
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