MariaDB 5.3.0 Release Notes
Release date: 26 July 2011
MariaDB 5.3.0 is a Beta release. In general this means that there are no known serious bugs, except for those marked as feature requests. MariaDB 5.3 radically improves performance for subqueries as well as for joins and single-table queries over large data sets.
For a list of every change made in MariaDB 5.3.0, including the various bugs that were fixed and links to detailed information on each push, see the MariaDB 5.3.0 Changelog. These changes are compared against MariaDB 5.2, and it is worth noting that MariaDB 5.3 is based on the MySQL 5.1 releases.
In most respects MariaDB will work exactly as MySQL: all commands, interfaces, libraries and APIs that exist in MySQL also exist in MariaDB.
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One of the major performance improvements in MariaDB 5.3.0 is that subqueries are finally usable in practice. It is no longer necessary to rewrite subqueries manually into joins or separate queries. The optimizer of MariaDB 5.3 will do this, and more automatically. EXPLAIN for derived tables and materialized views is instantaneous. Both derived tables and views can be optimized by indexes created on the fly.
Join & disk access optimizations
MariaDB now supports many join optimizations, including utilizing the Block Nested Loop algorithm that can be used for outer joins, Classic Hash Join which can be used for equi-joins, and Batch Key Access joins are supported providing the benefits of ordered retrievals for primary and secondary keys provided by the new implementation of Multi-Range-Read (MRR) optimizations. MariaDB also features Index Condition Pushdown.
Dynamic columns allows you to have a different set of "virtual columns" for each row in your table. You can at any time add or remove columns from a row.
Group commit for the binary log
MariaDB 5.3 implements group commit which works when using XtraDB with the binary log enabled.
Microsoft Windows performance improvements
Microsoft Windows performance improvements from MySQL 5.5 have been backported, including benefits to the XtraDB storage engine.