How to query relational data in ascending order in strapi?

Question

I have this query that works

  async find(ctx) {
    let { _start, _limit } = ctx.request.query;
    console.log(ctx.request.query)
    _limit ? 0 : (_limit = 10);
    const entities = await strapi.services["course-series"].find({});
    return entities.map((entity) => {
      // Do I sort them here or in the url query (and how)
      entity.courses = entity.courses.slice(_start, _limit);
      return sanitizeEntity(entity, { model: strapi.models["course-series"] });
    });
  }

The idea is that I can load 10 courses from each series at first and then get the next 10...

I just realized that the first 10 I am getting are not the recent ones.

As I commented // Do I sort them here or in the url query (and how)

Answer 1

What version of Strapi do you use? What does this line do strapi.services["course-series"].find({})? How did you build this find method in the service? What does it do? Does it accept params?

Personally I'd do something like that (assuming you're working with Strapi version > 4:

const entities = await strapi.entityService.findMany('api::course-series.course-series', {
  fields: [/* list the course-series fields you want to populate */],
  populate: {
    courses: {
      fields: [/* list the course fields you want to populate */],
      sort: 'createdAt:desc', // You can use id, publishedAt or updatedAt here, depends on your sorting prefrences
      offset: _start,
      limit: _limit // I must admit I haven't tested `offset` and `limit` on the populated related field
    }
  }
})

// ...the rest of your code, if needed

Read more about Entity Service API here.

Doing it the way you did it, you will always first retrieve the full list of courses for each course-series, and then run costly operations like mapping (the lesser of 2 evils) and above all sorting.