problem about second index on innodb

[h ch]

i see the following statement in manual

Each secondary index record also contains all the primary key fields defined for the clustered index key that are not in the secondary index.

that's mean the fields in cluster index will not be counted if they also belong to the second index?

say, i have table (c1,c2,v3,v4),if the cluster index on (c1,v3),when i create the second index on (v3,v4),the column v3 will not be stored twice??