Gorm Preloading with inner join with condition on nested table

Your Question

I have the following nested structure (simplified for clarity; I'm not actually dealing with fruits): A main Fruit table with a reference to a FruitData table that holds additional data about each fruit, which in turn has an optional AppleData table which holds additional data specific to apples.

type Fruit struct {
    gorm.Model
    FruitData FruitData
    FruitType int
}

type FruitData struct {
    gorm.Model
    FruitID       uint
    SourceCountry string
    AppleData     *AppleData
}

type AppleData struct {
    gorm.Model
    FruitDataID uint
    Seeds       int
}

I want to get a list of all apples with more than 4 seeds, while also preloading FruitData and FruitData.AppleData.

I could do it like this:

var fruits []Fruit
db.
    Joins("JOIN fruit_datas ON fruit_datas.fruit_id = fruits.id").
    Joins("JOIN apple_datas ON apple_datas.fruit_data_id = fruit_datas.id AND apple_datas.seeds > 4").
    Preload("FruitData").
    Preload("FruitData.AppleData").
    Find(&fruits)

However, this requires doing both joins and preloading, which is wasteful. Is there any way to do the same thing without having to use both Joins and Preload for the same tables?

The document you expected this should be explained

https://gorm.io/docs/advanced_query.html https://gorm.io/docs/preload.html

Expected answer

An example on how to get the requested preloaded entries without unnecessary queries.

Comment From: github-actions[bot]

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Comment From: saeidee

There are no unnecessary queries, the joins that you are using are part of the fetch Fruits query, and preloads are for preloading the relations.

With joins (3 queries)

Without joins (3 queries)