mysql> SHOW GLOBAL VARIABLES LIKE 'slow_query_log' We can also check the variable/parameters values as shown in listing 06. Slow-query-log-file = /var/log/mysql/mysql-slow.log The parameter changes are lost after MySQL reboots because the parameters are set dynamically, so in order to make the changes permanent, we need to set up the parameters in the MySQL configuration file ( /etc/mysql/my.cnf) as shown in listing 05.
#Mysql optimizer turn off full
While it’s important to log all queries that are not hitting indexes, it does not indicate a slow query because there are cases when the query optimizer chooses full table scan rather than using any available index for example, if the table is still small or we’re requesting more than 25% of the total rows. mysql> SET GLOBAL log_queries_not_using_indexes = 1 We can also indicate to log queries not using indexes, as shown in the listing 04. mysql> SET GLOBAL slow_query_log_file = '/var/log/mysql/mysql-slow.log' We can also set up another location as shown in listing 03 using the slow_query_log_file parameter. One strategy is to turn this setting on for a period of time and then revert it back to log only the slow queries.īy default, the slow query log file is located at /var/lib/mysql/hostname-slow.log. Be very careful while setting up long_query_time=0 because this setting will increase the I/O workload on your system (due to the writing operations) and your disk space can be filled up. It's recommended to set up long_query_time=0 in order to log all queries, because the first step is to analyze all the queries to find out the most commonly used and the slowest ones. We can change this setting to 5 seconds using the long_query_time parameter as shown in listing 02.
When the slow query log feature is enabled, by default MySQL logs any query that takes longer than 10 seconds to execute. The slow query log feature is turned off by default in MySQL, so in order to turn this feature on, we need to set the slow_query_log parameter to ON as shown in listing 01. After reading this article, you will be able to apply these concepts and techniques when you have an under-performing system.
#Mysql optimizer turn off how to
This feature is not activated by default, so in this article, I'll explain how to active this feature and how to analyze the results in order to discover the bottlenecks in the data pipeline. The queries in the slow query log are good candidates to start optimizing and eliminating the bottlenecks. The slow query log feature in MySQL allows you to log all queries that take longer than a given threshold of execution time. Query optimization is essential to ensure high performance for the most important queries. If you don't analyze, optimize, and tune the slow queries as early as possible, the overall performance of your system will eventually degrade. Slow queries can negatively impact database performance.
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