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mysql慢查詢操作實(shí)例分析【開啟、測(cè)試、確認(rèn)等】

發(fā)布時(shí)間：2020-10-01 04:32:34 來源：腳本之家 閱讀：157 作者：dawn-liu 欄目：MySQL數(shù)據(jù)庫(kù)

本文實(shí)例講述了mysql慢查詢操作。分享給大家供大家參考，具體如下：

mysql有些sql會(huì)執(zhí)行很慢，有可能造成服務(wù)器負(fù)載飆升

首先查詢 確定影響負(fù)載的是mysql ，使用top命令，ps命令等

其次，進(jìn)入MySQL，使用show full processlist查詢執(zhí)行中的sql語句，看看問題，使用explain 命令 查看狀態(tài)

最后找出sql語句殺死或者優(yōu)化

centos7上面安裝mariadb服務(wù)

yum -y install mariadb-server mariadb-devel

開啟慢查詢

more /etc/my.cnf.d/server.cnf
[mariadb]
slow_query_log=ON
slow_query_log_file=/usr/local/mysql/data/slow.log
long_query_time=1

啟動(dòng)mariadb服務(wù)

systemctl start mariadb

查詢mysql的慢查詢是否開啟，以及多久的時(shí)間以上是慢查詢

MariaDB [(none)]> show variables like '%slow_query%';
+---------------------+--------------------------------+
| Variable_name    | Value             |
+---------------------+--------------------------------+
| slow_query_log   | ON               |
| slow_query_log_file | /usr/local/mysql/data/slow.log |
+---------------------+--------------------------------+
2 rows in set (0.00 sec)

MariaDB [(none)]> show variables like 'long_query_time';
+-----------------+----------+
| Variable_name  | Value  |
+-----------------+----------+
| long_query_time | 1.000000 |
+-----------------+----------+
1 row in set (0.00 sec)


#如果沒用開啟慢查詢，可以在命令行開啟
mysql> set global slow_query_log=1;
Query OK, 0 rows affected (0.00 sec)

 測(cè)試慢查詢，以及查看日志

MariaDB [(none)]> select sleep(2);
+----------+
| sleep(2) |
+----------+
|    0 |
+----------+
1 row in set (2.00 sec)


[root@localhost ~]# more /usr/local/mysql/data/slow.log
/usr/libexec/mysqld, Version: 5.5.60-MariaDB (MariaDB Server). started with:
Tcp port: 0 Unix socket: /var/lib/mysql/mysql.sock
Time         Id Command  Argument
# Time: 180930 23:51:07
# User@Host: root[root] @ localhost []
# Thread_id: 2 Schema:  QC_hit: No
# Query_time: 2.001017 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 0
SET timestamp=1538322667;
select sleep(2);

 確認(rèn)慢查詢

MariaDB [(none)]> show full processlist; #查看state慢查詢?cè)谶M(jìn)行
+----+------+-----------+------+---------+------+------------+-----------------------+----------+
| Id | User | Host   | db  | Command | Time | State   | Info         | Progress |
+----+------+-----------+------+---------+------+------------+-----------------------+----------+
| 3 | root | localhost | NULL | Query  |  9 | User sleep | select sleep(10)   |  0.000 |
| 4 | root | localhost | NULL | Query  |  0 | NULL    | show full processlist |  0.000 |
+----+------+-----------+------+---------+------+------------+-----------------------+----------+
2 rows in set (0.00 sec)

MariaDB [(none)]> show full processlist; #查看state慢查詢已經(jīng)結(jié)束，但是用戶登陸了
+----+------+-----------+------+---------+------+-------+-----------------------+----------+
| Id | User | Host   | db  | Command | Time | State | Info         | Progress |
+----+------+-----------+------+---------+------+-------+-----------------------+----------+
| 3 | root | localhost | NULL | Sleep  |  1 |    | NULL         |  0.000 |
| 4 | root | localhost | NULL | Query  |  0 | NULL | show full processlist |  0.000 |
+----+------+-----------+------+---------+------+-------+-----------------------+----------+
2 rows in set (0.00 sec)

更多關(guān)于MySQL相關(guān)內(nèi)容感興趣的讀者可查看本站專題：《MySQL查詢技巧大全》、《MySQL常用函數(shù)大匯總》、《MySQL日志操作技巧大全》、《MySQL事務(wù)操作技巧匯總》、《MySQL存儲(chǔ)過程技巧大全》及《MySQL數(shù)據(jù)庫(kù)鎖相關(guān)技巧匯總》

希望本文所述對(duì)大家MySQL數(shù)據(jù)庫(kù)計(jì)有所幫助。

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