做MySQL性能調(diào)整和服務(wù)狀態(tài)監(jiān)控,有個(gè)前提就是我們要知道當(dāng)前MySQL的運(yùn)行狀態(tài). 很對(duì)開(kāi)發(fā)人員對(duì)分庫(kù)分表,讀寫(xiě)分離,SQL性能分析等或多或少有看過(guò)一些文章分析,但是如果不結(jié)合實(shí)際的MySQL運(yùn)行狀態(tài)盲目的做一些MySQL配置調(diào)整是一種大致加估計(jì)的做法,可能恰好切合了當(dāng)前的實(shí)際問(wèn)題有了性能提升,也有可能毫無(wú)作用. 所以,做技術(shù)還是要實(shí)際情況和理論結(jié)合,不能紙上談兵.

本文參考MySQL官方文檔: server-status-variables

我們可以使用語(yǔ)句SHOW [GLOBAL | SESSION] STATUS 來(lái)看全局/當(dāng)前會(huì)話(huà)的可查看狀態(tài)指標(biāo)

比如我們要看MySQL全局狀態(tài)指標(biāo)有那些可以使用

mysql> SHOW GLOBAL STATUS;+-----------------------------------+------------+| Variable_name | Value |+-----------------------------------+------------+| Aborted_clients | 0 || Aborted_connects | 0 || Bytes_received | 155372598 || Bytes_sent | 1176560426 |...| Connections | 30023 || Created_tmp_disk_tables | 0 || Created_tmp_files | 3 || Created_tmp_tables| 2 |...| Threads_created | 217 || Threads_running | 88 || Uptime | 1389872 |+-----------------------------------+------------+

如果你只對(duì)當(dāng)前你自己的連接感興趣那么可以使用SHOW SESSION STATUS

其中如果你想刷新?tīng)顟B(tài)變量的統(tǒng)計(jì)信息可以使用命令FLUSH STATUS

Many status variables are reset to 0 by the FLUSH STATUS statement.

依據(jù)上文查出的可以查詢(xún)的狀態(tài)變量,我選擇幾個(gè)變量做一些演示

查詢(xún)MySQL運(yùn)行的時(shí)間:

mysql> show status like ’uptime’;+---------------+--------+| Variable_name | Value |+---------------+--------+| Uptime | 398545 |+---------------+--------+1 row in set (0.01 sec)

查詢(xún)MySQL的select執(zhí)行次數(shù)

mysql> show global status like ’com_select’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Com_select | 19 |+---------------+-------+1 row in set (0.01 sec)

查詢(xún)MySQL的insert執(zhí)行次數(shù)

mysql> show status like ’com_insert’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Com_insert | 0 |+---------------+-------+1 row in set (0.00 sec)

查詢(xún)MySQL的update執(zhí)行次數(shù)

mysql> show status like ’com_update’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Com_update | 0 |+---------------+-------+1 row in set (0.00 sec)

查詢(xún)MySQL的delete執(zhí)行次數(shù)

mysql> show status like ’com_delete’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Com_delete | 0 |+---------------+-------+1 row in set (0.00 sec)

上面的CRUD次數(shù)統(tǒng)計(jì),可以直接的作為實(shí)際MySQL性能優(yōu)化的依據(jù).比如根據(jù)讀寫(xiě)的比例來(lái)調(diào)整內(nèi)存分配策略.

查詢(xún)連接次數(shù)

mysql> show status like ’connections’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Connections | 286 |+---------------+-------+1 row in set (0.00 sec)

查詢(xún)慢查詢(xún)次數(shù)

mysql> show status like ’slow_queries’;+---------------+-------+| Variable_name | Value |+---------------+-------+| Slow_queries | 0 |+---------------+-------+1 row in set (0.00 sec)

查詢(xún)慢查詢(xún)時(shí)間（默認(rèn)10秒）

mysql> show variables like ’long_query_time’;+-----------------+-----------+| Variable_name | Value |+-----------------+-----------+| long_query_time | 10.000000 |+-----------------+-----------+1 row in set (0.01 sec)

其實(shí)指標(biāo)有很多,當(dāng)遇到實(shí)際問(wèn)題后可以針對(duì)性的進(jìn)行查詢(xún)?nèi)缓笠罁?jù)這些數(shù)據(jù)做MySQL參數(shù)調(diào)整.

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