Replication: Previously, replication slaves could connect to the master server only through master accounts that use native authentication. Now replication slaves can also connect through master accounts that use nonnative authentication (except Windows native authentication) if the required client-side plugin is installed on the slave side in the directory named by the slave plugin_dir system variable. The exception for Windows is lifted in MySQL 5.5.19. (Bug #12897501)

MEMORY table creation time is now available in the CREATE_TIME column of the INFORMATION_SCHEMA.TABLES table and the Create_time column of SHOW TABLE STATUS output. (Bug #51655, Bug #11759349)

The make_win_bin_dist script is no longer used and has been removed from MySQL distributions and the manual. (Bug #58241)

Performance; InnoDB: This fix improves the performance of instrumentation code for InnoDB buffer pool operations. (Bug #12950803, Bug #62294)

InnoDB: Lookups using secondary indexes could give incorrect matches under a specific set of conditions. The conditions involve an index defined on a column prefix, for a BLOB or other long column stored outside the index page, with a table using the Barracuda file format. (Bug #12601439, Bug #12543666)

InnoDB: This fix corrects cases where the MySQL server could hang or abort with a long semaphore wait message. (This is a different issue than when these symptoms occurred during a CHECK TABLE statement.) (Bug #11766591, Bug #59733)

Internal conversion of zero to binary and back could yield a result with incorrect precision. (Bug #12911710)

Valgrind warnings generated by filesort operations were fixed. (Bug #12856915)

mysqld_safe did not properly check for an already running instance of mysqld. (Bug #11878394)

With Valgrind enabled, InnoDB semaphore wait timeouts were too low and could expire. (Bug #11765460)

The help message for mysql_install_db did not indicate that it supports the --defaults-file, --defaults-extra-file and --no-defaults options. (Bug #58898, Bug #11765888)

myisampack could create corrupt FULLTEXT indexes when compressing tables. (Bug #53646, Bug #11761180)

An assertion designed to detect zero-length sort keys also was raised when the entire key set fit in memory. (Bug #58200, Bug #11765254)

A linking problem prevented the FEDERATED storage engine plugin from loading. (Bug #40942, Bug #11750417)