MySQL index optimization

Catalog

Primary key optimization

  Page splitting

Page merge

Primary key design

 Order by

Limit Overlay index + Subquery  

 Count

 Update

---

Primary key optimization

  Page splitting

Insert in disorder id=50 when ,page=1 Will split in half , Move half to page=3 in , then id=50 Insert .

Page merge

 

 

Primary key design

 Order by

 

 

Limit Overlay index + Subquery  

SELECT * FROM xxx WHERE ID > =(select id from xxx limit 1000000, 1) limit 20;
SELECT * FROM xxx a JOIN (select id from xxx limit 1000000, 20) b ON a.ID = b.id;

 Count

 

count(1) and count(*) The best performance  

 Update

update The update of is a row level lock added to the index , Non index will be promoted to table lock .