MySQL Community Edition is a freely downloadable version of the world's most popular open source database that is supported by an active community of open source developers and enthusiasts.
MySQL delivers enterprise features, including:
- Partitioning to improve performance and management of very large database environments
- Row-based/Hybrid Replication for improved replication security
- Event Scheduler to create and schedule jobs that perform various database tasks
- XPath Support
- Dynamic General/Slow Query Log
- Performance/Load Testing Utility (mysqlslap)
- Improved! Full Text Search (faster, new dev templates)
- Improved! Archive engine (better compression, more features)
- Improved! User session and problem SQL identification
- Improved! MySQL embedded library (libmysqld)
- Additional INFORMATION_SCHEMA objects
- Faster data import operations (parallel file load)
- ACID Transactions to build reliable and secure business critical applications
- Stored Procedures to improve developer productivity
- Triggers to enforce complex business rules at the database level
- Views to ensure sensitive information is not compromised
- Information Schema to provide easy access to metadata
- Pluggable Storage Engine Architecture for maximum flexibility
- Archive Storage Engine for historical and audit data
# Bugs Fixed
* Security Fix: Bug #64884 was fixed.
* Security Fix: Bug #59387 was fixed.
* InnoDB: Deleting a huge amount of data from InnoDB tables within a short time could cause the purge operation that flushes data from the buffer pool to stall. If this issue occurs, restart the server to work around it. This issue is only likely to occur on 32-bit platforms.
* InnoDB: If the server crashed during a TRUNCATE TABLE or CREATE INDEX statement for an InnoDB table, or a DROP DATABASE statement for a database containing InnoDB tables, an index could be corrupted, causing an error message when accessing the table after restart:
- InnoDB: Error: trying to load index index_name for table table_name
- InnoDB: but the index tree has been freed!
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not the built-in InnoDB storage engine.
* InnoDB: When data was removed from an InnoDB table, newly inserted data might not reuse the freed disk blocks, leading to an unexpected size increase for the system tablespace or .ibd file (depending on the setting of innodb_file_per_table. The OPTIMIZE TABLE could compact a .ibd file in some cases but not others. The freed disk blocks would eventually be reused as additional data was inserted.
* Partitioning: After updating a row of a partitioned table and selecting that row within the same transaction with the query cache enabled, then performing a ROLLBACK, the same result was returned by an identical SELECT issued in a new transaction.
* Replication: The --relay-log-space-limit option was sometimes ignored.
More specifically, when the SQL thread went to sleep, it allowed the I/O thread to queue additional events in such a way that the relay log space limit was bypassed, and the number of events in the queue could grow well past the point where the relay logs needed to be rotated. Now in such cases, the SQL thread checks to see whether the I/O thread should rotate and provide the SQL thread a chance to purge the logs (thus freeing space).
Note that, when the SQL thread is in the middle of a transaction, it cannot purge the logs; it can only ask for more events until the transaction is complete. Once the transaction is finished, the SQL thread can immediately instruct the I/O thread to rotate.
* Mishandling of NO_BACKSLASH_ESCAPES SQL mode within stored procedures on slave servers could cause replication failures.
* If the system time was adjusted backward during query execution, the apparent execution time could be negative. But in some cases these queries would be written to the slow query log, with the negative execution time written as a large unsigned number. Now statements with apparent negative execution time are not written to the slow query log.
* mysql_store_result() and mysql_use_result() are not for use with prepared statements and are not intended to be called following mysql_stmt_execute(), but failed to return an error when invoked that way in libmysqld.
* SHOW statements treated stored procedure, stored function, and event names as case sensitive.
* On Windows, mysqlslap crashed for attempts to connect using shared memory.