Kysely•2w ago

Replicate ORM results

Hi guys, I wanted this result:

findPersonsWithPets: [
  {
    "id": 1,
    "first_name": "Peter",
    "last_name": "Carlsson",
    "age": 57,
    "created_at": "2025-02-08T08:09:35.320Z",
    "updated_at": null,
    "pets": [
      {
        "id": 1,
        "name": "Juni"
      },
      {
        "id": 5,
        "name": "Juni 2"
      }
    ]
  },
......

and did this and it's working but i wonder if there is a better way to do it?

export async function findPersonsWithPets() {
    const rows = await db
        .selectFrom('person')
        .leftJoin('pet', 'pet.owner_id', 'person.id')
        .select([
            'person.id',
            'person.first_name',
            'person.last_name',
            'person.age',
            'person.created_at',
            'person.updated_at',
            'pet.id as petId',
            'pet.name as petName'
        ])
        .orderBy('person.id') // Ensure results are grouped by person
        .execute();

    // Transform result into structured array
    const personsMap = new Map<
        number,
        {
            id: number;
            first_name: string;
            last_name: string;
            age: number;
            created_at: Date;
            updated_at: Date | null;
            pets: Array<{ id: number; name: string }>;
        }
    >();

    for (const row of rows) {
        if (!personsMap.has(row.id)) {
            personsMap.set(row.id, {
                id: row.id,
                first_name: row.first_name,
                last_name: row.last_name,
                age: row.age,
                created_at: row.created_at,
                updated_at: row.updated_at,
                pets: []
            });
        }
        if (row.petId) {
            personsMap.get(row.id)!.pets.push({ id: row.petId, name: row.petName ?? '' });
        }
    }

    return Array.from(personsMap.values());
}

Solution:

Hey 👋 Have you read https://kysely.dev/docs/recipes/relations ?...

Relations | Kysely

Kysely IS NOT an ORM. Kysely DOES NOT have the concept of relations.

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