3a9358a410
This patch introduces a new way of handling UPDATE and DELETE commands at the top level after the parsing phase. This new way of processing update and delete statements can be seen in the implementation of the prepare() and execute() methods from the new Sql_cmd_dml class. This class derived from the Sql_cmd class can be considered as an interface class for processing such commands as SELECT, INSERT, UPDATE, DELETE and other comands manipulating data in tables. With this patch processing of update and delete statements after parsing proceeds by the following schema: - precheck of the access rights is performed for the used tables - the used tables are opened - context analysis phase is performed for the statement - the used tables are locked - the statement is optimized and executed - clean-up is performed for the statement The implementation of the method Sql_cmd_dml::execute() adheres this schema. The virtual functions of the class Sql_cmd_dml used for precheck of the access rights, context analysis, optimization and execution allow to adjust this schema for processing data manipulation statements of any types. This schema of processing data manipulation statements is taken from the current MySQL code. Moreover the definition the class Sql_cmd_dml introduced in this patch is almost a full replica of such class in the existing MySQL. However the implementation of the derived classes for update and delete statements is quite different. This implementation employs the JOIN class for all kinds of update and delete statements. It allows to perform main bulk of context analysis actions by the function JOIN::prepare(). This guarantees that characteristics and properties of the statement tree discovered for optimization phase when doing context analysis are the same for single-table and multi-table updates and deletes. With this patch the following functions are gone: mysql_prepare_update(), mysql_multi_update_prepare(), mysql_update(), mysql_multi_update(), mysql_prepare_delete(), mysql_multi_delete_prepare(), mysql_delete(). The code within these functions have been used as much as possible though. The functions mysql_test_update() and mysql_test_delete() are also not needed anymore. The method Sql_cmd_dml::prepare() serves processing - update/delete statement - PREPARE stmt FROM "<update/delete statement>" - EXECUTE stmt when stmt is prepared from update/delete statement. Approved by Oleksandr Byelkin <sanja@mariadb.com> |
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Code status:
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MariaDB: The open source relational database
MariaDB was 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/new-and-old-releases/
Help
More help is available from the Maria Discuss mailing list https://launchpad.net/~maria-discuss, MariaDB's Zulip instance, https://mariadb.zulipchat.com/
Live QA for beginner contributors
MariaDB has a dedicated time each week when we answer new contributor questions live on Zulip. 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.
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/
The code for MariaDB, including all revision history, can be found at: https://github.com/MariaDB/server