The MariaDB project has announced the availability of MariaDB 5.3.3-rc, the first Release Candidate release in the 5.3 series. Several optimization features introduced in MariaDB 5.3 have been thoroughly tested, and switched on by default in 5.3.3.

Performance changes that has been worked:

• Subquery materialization (materialization=on)
• Semi-join optimizations (semijoin=on,firstmatch=on,loosescan=on)
• Derived table optimization (derived_merge=on,derived_with_keys=on -Documentation is being worked on-),
• Index Condition Pushdown (index_condition_pushdown=on)
• Nested loop join will use its Block-based variant more aggressively
• Block-based join for OUTER JOINs (outer_join_with_cache=on)
• Block-based join for semi-joins (semijoin_with_cache=on)
• Linked join buffers (more aggressive buffering of multi-way joins) (@@join_cache_level==2)

Also, DISTINCT and GROUP BY clauses are now removed from subqueries when possible. This allows for more efficient query plans. (backported from MySQL 5.6)

About the changes related to usability:

EXPLAIN  output has been improved in MariaDB 5.3.3 to be easier to understand:

• The select_type column now shows MATERIALIZED for subqueries that are executed with Materialization (it used to show SUBQUERY, which made it hard to distinguish  materialized subqueries from other kinds subqueries).

• For a Duplicate Elimination strategy, Start temporary is now shown at the first table from the subquery.

For a list of changes, about MariaDB 5.3, please read the following link:

Enjoy MariaDB!