Based on MySQL 5.5.14, including all the bug fixes in it, Percona Server 5.5.14-20.5 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 5.5.14-20.5 milestone at Launchpad.
fsync() has been replaced with fdatasync() to improve perfomance where possible. The former is intended to sync the metadata of the file also (size, name, access time, etc.), but for the transaction log and the doublewrite buffer, such sync of metadata isn’t needed. Bug Fixed: #803270 (Yasufumi Kinoshita).
Two new collations, utf8_general50_ci and ucs2_general50_ci, have been to improve compatibility for those upgrading from MySQL 5.0 or 5.1 prior to version 5.1.24.
A fix for a MySQL bug (#27877) introduced an incompatible change in collations in MySQL 5.1.24. If the following collations were used:
and any of the indexes contained the German letter “U+00DF SHARP S” ß (which became equal to s), when upgrading from 5.0 / 5.1.23 or lower:
- any indexes on columns in that situation must be rebuilt after the upgrade, and
- unique constrains may get broken after upgrade due to possible duplicates.
This problem is avoided when upgrading to Percona Server by converting the affected tables or columns to the collations introduced:
- utf8_general_ci to utf8_general50_ci, and
- ucs2_general_ci to ucs2_general50_ci.
Blueprint: utf8-general50-ci-5.5 (Alexey Kopytov).
- When adding a table to the cache, the server may evict and close another if the table cache is full. If the closed table was on the FEDERATED engine and a replication environment, its client connection to the remote server was closed leading to an unappropriated network error and stopping the Slave SQL thread. Bugs Fixed #813587 / #51196 and #61790 in MySQL (Alexey Kopytov).
- Querying global_temporary_tables caused the server to crash in some scenarios due to insufficient locking. Fixed by introducing a new mutex to protect from race conditions. Bug Fixed: #745241 (Alexey Kopytov).
- Using the innodb_lazy_drop_table option led to an assertion error when truncating a table in some scenarios. Bug Fixed: #798371 (Yasufumi Kinoshita).
Improvements and fixes on platform-specific distribution:
Improvements and fixes on general distribution:
Improvements and fixes on the Percona Server documentation: