how to query a self-reference like this

[799189288]

this is the entity

pub struct Model {
    #[sea_orm(primary_key, auto_increment = false)]
    pub id: Uuid,
    pub name: Option<String>,
    pub category_id: Option<Uuid>,
}
#[derive(Debug, Deserialize, Serialize)]
pub struct CategoryTree {
    #[serde(flatten)]
    pub category: Model,
    pub children: Vec<CategoryTree>,
}

and i want a tree struct like Vec<CategoryTree>

[799189288]

yeah, i finally find the resolution.
here is the answer:
1.first of all, you need to query all category and divide result into two part: one with parentid another without.
2.recursively find the children and assign the value.
i think this should be listed as a example.

pub async fn query_category(db: &DbConn) -> Result<Vec<category::TreeModel>, DbErr> {
        let categories: Vec<category::TreeModel> = category::Entity::find()
            .all(db)
            .await?
            .into_iter()
            .map(|i| i.into())
            .collect();
        let first_categories = categories
            .clone()
            .into_iter()
            .filter(|i| i.category.category_id.is_none())
            .collect();
        let left_categories = categories
            .into_iter()
            .filter(|i| i.category.category_id.is_some())
            .collect();
        let categories = Self::recur_category(first_categories, left_categories);
        Ok(categories)
    }
    pub fn recur_category(
        mut categories: Vec<category::TreeModel>,
        left_categories: Vec<category::TreeModel>,
    ) -> Vec<category::TreeModel> {
        if categories.len() == 0 {
            return categories;
        }
        for node in categories.iter_mut() {
            let sub_categories: Vec<category::TreeModel> = left_categories
                .clone()
                .into_iter()
                .filter(|i| i.category.category_id.unwrap() == node.category.id)
                .collect();
            let children = Self::recur_category(sub_categories, left_categories.clone());
            node.children = children;
        }
        categories
    }