如何在Gorm中正确执行部分更新？

I have some sort of virtual file system. List of folders, each folder contains files, and ACL. So structure looks like this:

type Model struct {
    ID        uint       `gorm:"primary_key" json:"id"`
}

type User struct {
    Model
    Name string
}

type Folder struct {
    Model
    Name string
}

type File struct {
    Model
    Name string
    FolderID      uint
    Folder        Folder
    Acl           []User `json:"acl" gorm:"many2many:file_acl"`
} 

It comes from frontend as full fledged JSON. It gets demarshalled. What happens next when I call Save(&file) it correctly stores File, creates record inside file_acl.

Also it updates Folder and Users.

Here comes my question - how to skip those dependent updates but retain autogenerated queries to update/insert into file_acl table?

To prevent cascade updates you should use association_autoupdate option.

Db.Set("gorm:association_autoupdate", false).Save(&file)

I think you might want db.Set("gorm:save_associations", false).Save(...)