系統性能相關的MySQL變量 原文摘錄自：http://forge.mysql.com/wiki/ServerVariables Memory-Related Variables 內存相關變量 These server variables control the amount of memory allocated to the various buffers and caches within MySQL. 以下這些服

系統性能相關的MySQL變量

原文摘錄自：http://forge.mysql.com/wiki/ServerVariables

Memory-Related Variables
內存相關變量

These server variables control the amount of memory allocated to the various buffers and caches within MySQL.
以下這些服務器變量控制這MySQL分配給各種緩沖或者換緩存的內存總數。

join_buffer_size
(PER SESSION) Controls the amount of memory allocated to perform joins on tables that have no keys which can be used to perform a condition filter. Allocated for each table joined without necessary filter conditions
(會話變量) 控制在對沒有索引的表連接時分配的內存總數，它可以用做條件過濾器。為連接中的每個表分配而無需必要的過濾條件。

key_buffer_size
(GLOBAL) (MyISAM-only) Controls the amount of memory allocated to the MyISAM index key cache
(全局變量) (只針對MyISAM表) 空置分配給MyISAM索引緩存的內存總數。

innodb_buffer_pool_size
(GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the InnoDB cache containing both clustered data and secondary index pages
(全局變量) (只針對Innodb) 控制分配給包括集群數據以及次要索引頁的Innodb緩存的內存總數。

innodb_additional_mem_pool_size
(GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the buffer storing the InnoDB internal data dictionary
(全局變量) (只針對Innodb) 控制分配給對Innodb內部數據字典進行排序所需的緩沖。

innodb_log_buffer_size
(GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the buffer storing InnoDB write-ahead log entries
(全局變量) (只針對Innodb) 控制分配給對Innodb存儲提前寫日志記錄所需的緩沖。

query_cache_size
(GLOBAL) Controls the amount of memory allocated to the Query Cache
(全局變量) 控制分配給查詢緩存的內存總量。

read_buffer_size
(PER SESSION) Controls the amount of memory allocated to the connecting thread in order to process a table scan
(會話變量) 控制分配給處理掃描表的連接線程內存總數。

read_rnd_buffer_size
(PER SESSION) Controls the amount of memory allocated to the buffer used to read previously sorted results
(會話變量) 控制分配給讀取當前排序完的結果所需的緩沖總數。

sort_buffer_size
(PER SESSION) Controls the amount memory allocated to the buffer used to sort result sets before returning the set to the calling client
(會話變量) 控制在把結果返回給調用的客戶端之前需要對結果集進行排序所需的緩沖總數。

thread_stack
(PER SESSION) Controls the default stack memory allocated for each connecting thread
(會話變量) 控制分配給每個連接線程的默認堆棧內存總數。

tmp_table_size
(GLOBAL) Controls the maximum memory to allocate to a temporary table before MySQL converts it into an on-disk MyISAM table
(全局變量) 控制MySQL在把一個臨時表轉換成磁盤存儲的MyISAM表時所需的最大內存總數。

Thread-Related Variables
線程相關變量

thread_cache_size
(GLOBAL) Determines the number of thread connection objects that MySQL keeps in a cache to mitigate resource creation costs
(全局變量) 確定MySQL在緩存中保持的連接線程數量，這能減少創建連接時所需的系統資源。

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