MySQL5.5.19 was released. three new functions were added to fix 6 BUG_MySQL

MySQL5.5.19 was released. three new features were added to fix six bugs: bitsCN.com.

MYSQL is mostly used in website production databases. And PHP and APACHE. Constitute the LMAP architecture.

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New Feature

• By creating a cache for the metadata lock object, the performance of the metadata lock operation in Windows XP is improved, which allows the server to avoid high-cost operations for creating and destroying the synchronization object in XP.
• A new system variable metadata_locks_cache_size is added, allowing you to control the cache size. the default size is 1024.
• Copy: before that, the master/slave server uses a non-local authenticated master account to copy the connection. It is also applicable to Windows local authentication.

Bug fixes

• InnoDB storage engine: When the buffer for DML operations is greatly changed, especially when the DELETE statement is used, server deadlocks may occur.
• DBL_MAX returns DBL_MAX instead of "inf ".
• When the -- write-binlog or -- skip-write-binlog option is used for running, mysql_upgrade does not upgrade the system table or create the mysql_upgrade_info file.
• If a plug-in is uninstalled, local variables of the string type variables marked with PLUGIN_VAR_MEMALLOC are not released.

? InnoDB Storage Engine: An internal deadlock cocould occur within InnoDB, on a server doing a substantial amount of change buffering for DML operations, and particle DELETE statements. (Bug #13340047)
? InnoDB Storage Engine: (Bug #12884631, Bug #62146)
? Rounding DBL_MAX returned DBL_MAX, not 'inf '. (Bug #13261955)
? Mysql_upgrade did not upgrade the system tables or create the mysql_upgrade_info file when run with the -- write-binlog or -- skip-write-binlog option. (Bug #60223, Bug #11827359)
? If a plugin was uninstalled, thread local variables for plugin variables of string type with wth PLUGIN_VAR_MEMALLOC flag were not freed. (Bug #56652, Bug #11763882)
? Deadlock cocould occur when these four things happened at the same time: 1) An old dump thread was waiting for the binary log to grow. 2) The slave server that replicates from the old dump thread tried to reconnect. during reconnection, the new dump thread tried to kill the old dump thread. 3) a kill statement tried to kill the old dump thread. 4) An INSERT statement caused a binary log rotation. (Bug #56299, Bug #11763573)

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