mjwebhosting
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- Joined
- Jun 18, 2011
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- 32
there is a new version for mysql 5.5
I have sent directadmin a email message if they want to add it to custombuild.
Code:
The default thread-handling model in MySQL Server executes statements using one thread per client connection. As more clients connect to the server and execute statements, overall performance degrades. Commercial distributions of MySQL now include a thread pool plugin that provides an alternative thread-handling model designed to reduce overhead and improve performance. The plugin implements a thread pool that increases server performance by efficiently managing statement execution threads for large numbers of client connections.
The thread pool addresses several problems of the one thread per connection model:
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Too many thread stacks make CPU caches almost useless in highly parallel execution workloads. The thread pool promotes thread stack reuse to minimize the CPU cache footprint.
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With too many threads executing in parallel, context switching overhead is high. This also presents a challenging task to the operating system scheduler. The thread pool controls the number of active threads to keep the parallelism within the MySQL server at a level that it can handle and that is appropriate for the server host on which MySQL is executing.
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Too many transactions executing in parallel increases resource contention. In InnoDB, this increases the time spent holding central mutexes. The thread pool controls when transactions start to ensure that not too many execute in parallel.
On Windows, the thread pool plugin requires Windows Vista or newer. On Linux, the plugin requires kernel 2.6.9 or newer.
For more information, see Section 7.11.6, “The Thread Pool Plugin”.
Pluggable Authentication Notes
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Commercial distributions of MySQL now include two plugins that enable MySQL Server to use external authentication methods to authenticate MySQL users:
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PAM (Pluggable Authentication Modules) enables a system to access various kinds of authentication methods through a standard interface. A PAM authentication plugin enables MySQL Server to use PAM to authenticate MySQL users.
The PAM plugin uses the information passed to it by the MySQL server (such as user name, host name, password, and authentication string), plus whatever is available for PAM lookup (such as Unix passwords or an LDAP directory). The plugin checks the user credentials against PAM and returns success or failure.
The PAM authentication plugin has been tested on Linux and Mac OS X.
Note
The PAM plugin works with a client-side plugin that simply sends the password to the server in clear text so it can be passed to PAM. This may be a security problem in some configurations, but is necessary to use the server-side PAM library. To avoid problems if there is any possibility that the password would be intercepted, clients should connect to MySQL Server using SSL. See Section 5.5.6.3, “The Clear Text Client-Side Authentication Plugin”.
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Distributions of MySQL for Windows include an authentication plugin that enables MySQL Server to use native Windows services to authenticate client connections. Users who have logged in to Windows can connect from MySQL client programs to the server based on the information in their environment without specifying an additional password.
The client and server exchange data packets in the authentication handshake. As a result of this exchange, the server creates a security context object that represents the identity of the client in the Windows OS. This identity includes the name of the client account. The Windows authentication plugin uses the identity of the client to check whether it is a given account or a member of a group. By default, negotiation uses Kerberos to authenticate, then NTLM if Kerberos is unavailable.
The Windows authentication plugin should work on Windows 2000 Professional
These authentication plugins enable MySQL Server to accept connections from users defined outside the MySQL grant tables. They also support the MySQL proxy-user capability. Each plugin can return to MySQL a user name different from the login user, which means that the plugin can return the MySQL user that defines the privileges the externally authenticated user should have. For example, an external user named joe can connect and have the privileges of the MySQL user named developer.
The server-side PAM and Windows authentication plugins are included only in commercial distributions. They are not included in MySQL community distributions. The client-side plugins with which they communicate are included in all distributions, including community distributions. This permits clients from any release to connect to a server that has the server-side plugin loaded.
For more information about these plugins, see Section 5.5.6.5, “The PAM Authentication Plugin”, and Section 5.5.6.6, “The Windows Native Authentication Plugin”. For general information about pluggable authentication in MySQL, see Section 5.5.6, “Pluggable Authentication”. For proxy user information, see Section 5.5.7, “Proxy Users”.
Functionality Added or Changed
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Important Change: Replication: The RESET SLAVE statement has been extended with an ALL keyword. In addition to deleting the master.info, relay-log.info, and all relay log files, RESET SLAVE ALL also clears all connection information otherwise held in memory following execution of RESET SLAVE. (Bug #11809016)
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A new utility, mysql_plugin, enables MySQL administrators to manage which plugins a MySQL server loads. It provides an alternative to manually specifying the --plugin-load option at server startup or using the INSTALL PLUGIN and UNINSTALL PLUGIN statements at runtime. See Section 4.4.5, “mysql_plugin — Configure MySQL Server Plugins”.
Bugs Fixed
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InnoDB Storage Engine: The “random read-ahead” feature that was removed from the InnoDB Plugin is now available again. Because it is only helpful for certain workloads, it is turned off by default. To turn it on, enable the innodb_random_read_ahead configuration option. Because this feature can improve performance in some cases and reduce performance in others, before relying on this setting, benchmark both with and without the setting enabled. (Bug #12356373)
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The metadata locking subsystem added too much overhead for INFORMATION_SCHEMA queries that were processed by opening only .frm or .TRG files and had to scan many tables. For example, SELECT COUNT(*) FROM INFORMATION_SCHEMA.TRIGGERS was affected. (Bug #12828477)
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Compilation failed on Mac OS X 10.7 (Lion) with a warning: Implicit declaration of function 'pthread_init' (Bug #12779790)
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With profiling disabled or not compiled in, set_thd_proc_info() unnecessarily checked file name lengths. (Bug #12756017)
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A DBUG_ASSERT added by Bug #11792200 was overly aggressive in raising assertions. (Bug #12537160)
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CHECK TABLE and REPAIR TABLE failed to find problems with MERGE tables that had underlying tables missing or with the wrong storage engine. Issues were reported only for the first underlying table. (Bug #11754210)
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Replication: Processing of corrupted table map events could cause the server to crash. This was especially likely if the events mapped different tables to the same identifier, such as could happen due to Bug#56226.
Now, before applying a table map event, the server checks whether the table has already been mapped with different settings, and if so, an error is raised and the slave SQL thread stops. If it has been mapped with the same settings, or if the table is set to be ignored by filtering rules, there is no change in behavior: the event is skipped and IDs are not checked. (Bug #44360, Bug #11753004)
See also Bug #11763509.
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For a lower_case_table_names value of 1 or 2 and a database having a mixed-case name, calling a stored function using a fully qualified name including the database name failed. (Bug #60347, Bug #11840395)
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Previously, Performance Schema table columns that held byte counts were BIGINT UNSIGNED. These were changed to BIGINT (signed). This makes it easier to perform calculations that compute differences between columns. (Bug #59631, Bug #11766504)
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The embedded server crashed when argc = 0. (Bug #57931, Bug #12561297)
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The mysql_affected_rows() C API function returned 3 (instead of 2) for INSERT ... ON DUPLICATE KEY UPDATE statements where there was a duplicated key value. (Bug #46675, Bug #11754979)
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Upgrades using an RPM package recreated the test database, which is undesirable when the DBA had removed it. (Bug #45415, Bug #11753896)I have sent directadmin a email message if they want to add it to custombuild.
