Gorm: Nested preloading

[nkovacs]

I'd like to do something like this, but I don't think it's possible:

type City struct {
    Id int
    Name string
}

type Address struct {
    HouseNumber int
    Street string

    City City
    CityId int
}

type Order struct {
    Address Address
    AddressId int

    User User
    UserId int
}

type User struct {
    Id int

    Orders []Order
}

db.Model(user).Preload("Address").Preload("Address.City").Related(&orders) // Address.City is not a relation in Order, so it's ignored

[jinzhu]

Hi @nkovacs

Yes, this is not supported yet, but on the plan already.

[rebyn]

:+1: would be lovely if gorm supports this.

[egeozcan]

I'm also looking forward to this. Any cues/ideas on how the api will be?

[jinzhu]

It will like @nkovacs's example.

db.Model(user).Preload("Address").Preload("Address.City").Related(&orders)

[dimascyriaco]

That would be really useful.

[rtm7777]

@jinzhu Can you confirm, this feature is working now?
https://github.com/jinzhu/gorm#nested-preloading

If it works, I think we also can update http://stackoverflow.com/questions/29230261/how-preload-a-full-hierachy-in-go-using-gorm

[jinzhu]

Hi @rtm7777

Yes, it is works already. sorry forgot to update this issue.

[benguild]

Keep in mind that this implementation uses subsequent SELECT(s). While this is great for simplicity (and perhaps multi-level caching with the correct callback configuration) ... it's also could be optimized by using JOIN statements to reduce latency to/from the server from multiple queries.

[dhruvak233]

@jinzhu Let the take the above example. Assume there is another level province which is under city.
Can we preload province under User without pre loading address and city