Aggregate on Relations

The following uses the test-vona module as an example to explain how to use Aggregate on Relations

For example, the User model and the Post model have a 1:n relation. When querying User data, we can query the aggregated data for the corresponding Post based on the relation

Dynamic Relation

class ServiceUser {
  async relationAggregate() {
    const users = await this.scope.model.user.select({
      with: {
        posts: $relationDynamic.hasMany(() => ModelPost, 'userId', {
          aggrs: {
            count: '*',
            sum: 'stars',
          },
        }),
      },
    });
    return users;
  }
}

Vona ORM automatically infers the type of users

Name	Description
with.posts	Relation Name
$relationDynamic.hasMany	1:n
ModelPost	Target Model
'userId'	Foreign key
aggrs	The functions and columns to be aggregated. Functions: count/sum/avg/min/max. Columns: string/string[]

Static Relation

1. Define the relation

For demonstration purposes, create a new Model UserStats and define a static relation posts

@Model({
  entity: EntityUser,
  relations: {
    posts: $relation.hasMany(() => ModelPost, 'userId', {
      aggrs: {
        count: '*',
        sum: 'stars',
      },
    }),
  },
})
class ModelUserStats {}

2. Using relations

class ServiceUser {
  async relationAggregate() {
    const users = await this.scope.model.userStats.select({
      include: {
        posts: true,
      },
    });
    return users;
  }
}

Vona ORM automatically infers the type of users

autoload

You can also set the static relation to autoload: true to achieve automatic loading, which can also further simplify the code

1. Define the relation

@Model({
  entity: EntityUser,
  relations: {
    posts: $relation.hasMany(() => ModelPost, 'userId', {
+     autoload: true,
      aggrs: {
        count: '*',
        sum: 'stars',
      },
    }),
  },
})
class ModelUserStats {}

2. Using relations

class ServiceUser {
  async relationAggregate() {
    const users = await this.scope.model.userStats.select();
    return users;
  }
}