MySQL Slow query1. What is the use of slow queries?It records all SQL statements that execute more than long_query_time time, helping you to find SQL that executes slowly, so we can optimize these SQL.2. How do I turn on slow queries?First we check if the MySQL server's slow query status is turned on.execute the following command:
we can see that the current log_slow_queries status is off, indicating that no slow query is currently turned on.It is very simple to turn on slow queries, as follows:Method One: Locate the MySQL configuration file my.cnf (/ETC/MY.CNF) and add the configuration statement for the slow query below mysqld (Note: Be sure to join below [mysqld], if it is in [Mysqld_safe] The following configuration statements are not valid. I have made this mistake during the configuration process and experienced the pain!)
Log-slow-queries: On behalf of the MySQL slow query log storage directory, this directory file must have write permissions.long_query_time: Maximum execution time. (, MSYQL will record all the execution time more than 2 SQL statements, here is the test time, the time should not be too small preferably within 5-10 seconds, of course, according to their own standards);configure it to restart a mysql later:Service mysqld Restartmethod Two: Perform the following operations on the MySQL command line: (Solve ing)
set the state of the MySQL variable by using the SET command. But my test never passed, and I suspect it could be a MySQL version of the problem.www.2cto.com
Online to find a lot of information, but have not been resolved, I hope the master can help me answer.after the configuration is complete, let's look at the current status again, and you'll find the following:
indicates that the slow query service has been turned on and the time limit is 2 seconds.Let's take a look at whether the Mysql-slow.log file is automatically created under the/var/lib/mysql/directory.
the cat mysql-slow.log discovery file already exists. Only the file does not have a task SQL record. So now let's test the execution of an SQL statement that is more than Long_query_time .
after executing a 3-second SQL statement, the SQL statement should be logged in the Mysql-slow.log file without exception. Ok! We cat mysql-slow.log a bit.
sure enough. The entire configuration process for slow queries is complete. reprinted from Http://www.2cto.com/database/201207/143358.html
MySQL Slow Query configuration
