mysql query 성능

1. explain

• extra 컬럼
  • using filesort ( https://www.percona.com/blog/2009/03/05/what-does-using-filesort-mean-in-mysql/ )
    • First of all, this is Using temporary
    • econdly, temporary tables may go to disk if they are too big, but EXPLAIN doesn’t show that.
  • using where. 이건 where 를 통해서 갯수가 제한되는 상황이면 보이는 것 같음

2. profiling

SET profiling = 1; // 활성화 
SET profiling = 0; // 비활성화
SHOW PROFILES;
show profile all for query 1;

3. optimizer_trace

show variables like 'optimizer_trace'
set optimizer_trace = 'enabled=on'

쿼리

select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE