Improve Performance of Grails Queries in MySQL

A web application that I was developing would become extremely slow as the number of requests increased per minute. I couldn't figure out why because with my local database everything seemed fine. Here is the process that I used in MySQL to determine the bottleneck in my database. The final problem was a missing index on a table that was used in the where clause of a select statement over and over again. I included a snapshot the MySQL Process list at the end of the post. Hope this helps someone.

Steps to Follow:

  • show full processlist;
    • shows each database connection that has been allocated for your database
    • contains the time a connection has been Sleep
    • contains how long a Query is taking to execute, you want this to be less than a second ideally
  • describe <query>;
    • this gives you the database's plan for executing the query
    • you want the number of rows that will be looked at to be as small as possible
  • show index from <table>;
    • this will list all indices contained on a table
    • this is a quick way to discover if you are missing a key index that could improve query performance
  • create index <tablename_fieldname_idx> on <table>(field);
    • this will add a new index to a table