How do I fix slow queries in MySQL?
MySQL has a built-in slow query log. To use it, open the my. cnf file and set the slow_query_log variable to “On.” Set long_query_time to the number of seconds that a query should take to be considered slow, say 0.2. Set slow_query_log_file to the path where you want to save the file.
What is MySQL slow log?
The MySQL slow query log is where the MySQL database server registers all queries that exceed a given threshold of execution time. This can often be a good starting place to see which queries are slowest and how often they are slow. MySQL on your server is configured to log all queries taking longer than 0.1 seconds.
How do I enable slow log query in MySQL?
Enable the Slow Query Log
- Log in to your server as the root user via SSH.
- Open the my.cnf file with a text editor and add the following block of code under the mysqld section: …
- Create the /var/log/mysql-slow.log file and set its user as the mysql user. …
- Restart MySQL or MariaDB. …
- Start monitoring the slow query logfile.
Why is MySQL query so slow?
If the data has tons of fields and rows, “select all” will tax the database resources and slow the entire system down. Your query will grind to a halt: data overload. This allows you to query only the fields that contain the needed information. “Defining your asterisk” should speed things up immediately.
What makes a query slow?
Slow queries can mean your database does more work than it needs to, which means it’s using more resources than it needs to. When limited resources like CPU or I/O run out, everything can start to slow down. Inefficient use of resources is also a problem when you’re not using the resources you have.
What is log file in MySQL?
MySQL Server has several logs that can help you find out what activity is taking place. … By default, the server writes files for all enabled logs in the data directory. You can force the server to close and reopen the log files (or in some cases switch to a new log file) by flushing the logs.
Where is my MySQL CNF file?
By default and on single instance MySQL servers you are most likely to find this file called my. cnf and found at:
- /etc/my. cnf.
- /etc/mysql/my. cnf.
How do I view MySQL logs?
How to show the queries log in MySQL?
- Enable Query logging on the database. SET global general_log = 1; SET global log_output = ‘table’;
- Now you can view the log by running this query: SELECT * FROM mysql. general_log;
- If you want to disable query logging on the database, run this query: SET global general_log = 0;
How do I check if a slow query log is enabled?
To enable the slow query log, type the following command at the mysql> prompt: SET GLOBAL slow_query_log = ‘ON’; There are additional options that you can set for the slow query log: By default, when the slow query log is enabled, it logs any query that takes longer than 10 seconds to run.
How do you find a slow query?
7 Ways to Find Slow SQL Queries
- Generate an Actual Execution Plan. …
- Monitor Resource Usage. …
- Use the Database Engine Tuning Advisor. …
- Find Slow Queries With SQL DMVs. …
- Query Reporting via APM Solutions. …
- SQL Server Extended Events. …
- SQL Azure Query Performance Insights.
How do I find slow MySQL queries?
To simplify examining the queries in a long slow query log, you can use mysqldumpslow command on some versions of MySQL. Queries that do not use indexes can also be logged in the slow query log by including the — log-queries-not-using-indexes option.
Does slow query log affect performance?
It is safe to log slow queries with execution time bigger than a second without worry about performance impact in case of CPU-bound workload. The performance impact is negligibly small in IO-bound workload even if all queries are logged.
What is query time in MySQL?
MySQL by default shows the time taken by the query to execute. Whenever you run a valid query, you will see the time of execution in seconds. … Once executed, you can check the query execution time using the below query: show profiles; You will be able to see the duration of query execution in seconds.