Based on MySQL 5.5.27, including all the bug fixes in it, Percona Server 5.5.27-28.0 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release can be found in the 5.5.27-28.0 milestone at Launchpad.
- Percona Server supports tunable buffer size for fast index creation in InnoDB. This value was calculated based on the merge block size (which was hardcoded to 1 MB) and the minimum index record size. By adding the session variable innodb_merge_sort_block_size block size that is used in the merge sort can now be adjusted for better performance.
- Percona Server has implemented ability to have a MySQL Utility user who has system access to do administrative tasks but limited access to user schema. This feature is especially useful to those operating MySQL As A Service.
- New Expanded Program Option Modifiers have been added to allow access control to system variables.
- New table INNODB_UNDO_LOGS has been added to allow access to undo segment information. Each row represents an individual undo segment and contains information about which rollback segment the undo segment is currently owned by, which transaction is currently using the undo segment, and other size and type information for the undo segment. This information is ‘live’ and calculated for each query of the table.
- Fixed incorrect merge of MySQL bug #61188 fix which caused server to freeze with “has waited at buf0buf.c line 2529 for XXX seconds the semaphore” errors. This regression was introduced in Percona Server 5.5.23-25.3. Bug fixed #1026926 (Stewart Smith).
- Fixed regression introduced in Percona Server 5.5.23-25.3 when merging the upstream fix for MySQL bug #64284. Bug fixed #1015109 (Stewart Smith).
- Fixed the upstream MySQL bug #66301. Concurrent INSERT ... ON DUPLICATE KEY UPDATE statements on a table with an AUTO_INCREMENT column could result in spurious duplicate key errors (and, as a result, lost data due to some rows being updated rather than inserted) with the default value of innodb_autoinc_lock_mode=1. Bug fixed #1035225 (Alexey Kopytov).
- Removed error log warnings that occured after enabling innodb_use_sys_stats_table and before ANALYZE TABLE is run for each table. Bug fixed #890623 (Alexey Kopytov).
- Removed the unneeded lrusort.py script. The server now does this sorting automatically and has done for some time. Bug fixed #882653 (Stewart Smith).
- Fixed the malformed CHANGE MASTER query in the output of mysqldump with --include-master-host-port option. Bug fixed #1013432 (Stewart Smith).
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