All indexes other than the clustered index are known as secondary indexes. In InnoDB, each record in a secondary index contains the primary key columns for the row, as well as the columns specified for the seconda ns for the row, as well as the columns specified for the seconda ns for the row as well as the columns specified for the secry sindex. search for the row in the clustered index.
All indexes other than the clustered index are known as secondary indexes. In InnoDB, each record in a secondary index contains the primary key columns for the row, as well as the columns specified for the seconda ns for the row, as well as the columns specified for the seconda ns for the row as well as the columns specified for the secry sindex. search for the row in the clustered index.
這個是官方文件中的，意思是secondary index也會包含primary,所以你主鍵越大，secondary indexes空間佔用也越大
參考：https://dev.mysql.com/doc/ref...