Analyzing the slow-query-log using tools like mysqldumpslow, pt-query-digest, and mysqlsla can provide valuable insights into the performance of your MySQL database. Here's a step-by-step guide on how to use these tools:
1. Enable slow-query-log:
- Uncomment the following lines in
/etc/mysql/my.cnf:
slow-query-log = 1
slow-query-log-file = /var/log/mysql/mysql-slow.log
long_query_time = 1
log-queries-not-using-indexes
- Adjust
long_query_timebased on your server's performance and the expected execution time of queries.
2. Collect slow query logs:
- Let the server run with the slow query log enabled for some time to collect data.
3. Analyze slow query logs:
Using mysqldumpslow:
- Command to show top 5 queries returning maximum rows:
mysqldumpslow -a -s r -t 5 /var/log/mysql/mysql-slow.log
- Command to sort output by count (frequency of occurrence) of queries:
mysqldumpslow -a -s c -t 5 /var/log/mysql/mysql-slow.log
Using pt-query-digest:
- Basic command to analyze slow query logs:
pt-query-digest /var/log/mysql/mysql-slow.log
- Filter queries for a specific database:
pt-query-digest /var/log/mysql/mysql-slow.log --filter '$event->{db} eq "db_wordpress"'
Using mysqlsla:
- Basic command to analyze slow query logs
./mysqlsla /var/log/mysql/mysql-slow.log
- Filter queries for a specific database:
./mysqlsla /var/log/mysql/mysql-slow.log -mf "db=db_name"
4. Interpretation and Action:
- Review the output of the analysis tools to identify slow queries, their frequency, and potential performance bottlenecks.
- Investigate queries that are returning a large number of rows or have a high frequency of occurrence.
- Optimize slow queries by adding indexes, rewriting queries, or optimizing database schema.
- Monitor the performance after optimizations and fine-tune as necessary.
By following these steps and using the provided tools, you can effectively analyze and optimize the performance of your MySQL database, especially in scenarios like debugging WordPress plugins or identifying performance issues in large-scale applications.
