duplicated preloads List duplicated records in mysql with gorm

[Chaunhewie]

problem

consider the following struct

struct A {
    ID string `gorm:"type:varchar(255)"`
    BID string `gorm:"type:varchar(255)"`
    b B `gorm:"foreignkey:BID"`
}
struct B {
    ID string `gorm:"type:varchar(255)"`
    cs []*C `gorm:"foreignkey:BID"`
}
struct C {
    ID string `gorm:"type:varchar(255)"`
    BID string `gorm:"type:varchar(255)"`
}

When I using query to list A's records, preloadEverything function in gorm/fields.go will find out preloads for B and B.C; however, when gorm preloads B, it will preload C in preload function which is after query function, and preloadMap will get B and C as key, and then return. As key C != key B.C, so gorm will preload C again, and gets duplicated C's records for B.cs

confused

When I checked preloadEverything function, I am really confused for subpreload as sf.Name has also been put into toPreload function (which means subpreload will be done when gorm preload sf.Name).
So why need to preload subpreload?

Solution

I just preload sf.Name and remove subpreload and the problem of duplicated records is solved.