[Question] How to serialize query results?

[hugotox]

Hello!

This might be an issue related to Svelte, but I still think is worth asking the difference, or why a knex query result is serializable and an objection is not.

Example on a +page.server.ts in Svelte:

import { Model } from 'objection'
import knex from 'knex'

const pg = knex({
  client: 'pg',
  connection: process.env.DATABASE_URL,
  searchPath: ['public'],
})

Model.knex(pg)

class User extends Model {
  static get tableName() {
    return 'users'
  }
}

export const load = async () => {
  const users = await User.query()
  return {
    users,
  }
}

The above code fails on Svelte with a Cannot stringify arbitrary non-POJOs error. I can circumvent this issue with users: users.map((u) => u.toJSON()), but seems inefficient for large resultsets.

What is most curious to me, is that a knex query works without parsing to JSON:

import knex from 'knex'

const pg = knex({
  client: 'pg',
  connection: process.env.DATABASE_URL,
  searchPath: ['public'],
})

export const load = async () => {
  const rawUsers = await pg.select('*').from('users')
  return {
    rawUsers,
  }
}

Any advice on how to properly use Objection in Svelte is highly appreciated 🙏

[yayza]

That's pretty much the most straightforward and simplest way to do it, it's how I do it using SvelteKit. Since model queries return models as result we'll have to transform them to JSON.

If you're working with large dataset, then I would suggest paginating results or streaming.

If you want to abstract away always using the map method on results you can create a custom QueryBuilder and add a new method .toJson() to it and chain that to your query:

export class CustomQueryBuilder<M extends Model, R> extends Model.QueryBuilder<M, R> {
    toJson() {
        return this.runAfter((result: any) => {
            if (Array.isArray(result)) {
                return result.map((r) => r.toJSON());
            } else if (result) {
                return result.toJSON();
            }
            return result;
        });
    }
}

export class BaseModel extends Model {
    static idColumn: string | string[] = "id";

    id: number;
    created_at: string;
    updated_at: string;

    static get QueryBuilder() {
        return CustomQueryBuilder;
    }

And you can use it like:

const queryResultsInJson = await BaseModel.query().toJson();