Query on Join Fields

[daohall]

Hi, is there any way to query a collection by filtering on the join field?
For example, I have a bi-directional relationship for category and posts

export const MyJoinField: Field = {
  name: 'relatedPosts',
  type: 'join',
  collection: 'posts',
  on: 'category',
}

// relationship field in another collection:
export const MyRelationshipField: Field = {
  name: 'category',
  type: 'relationship',
  relationTo: 'categories',
}

How do I query for categories that the "relatedPosts" is not empty?
I tried something like

const categoriesWithPosts = await payload.find({
  collection: 'categories',
  depth: 1,
  limit,
  where: { relatedPosts: { exists: true } },
});

but this is giving error Error: syntax error at or near "not". None of other filters like equals, in etc works.

If I try with filters like "relatedPosts.doc", it is giving the error Error: The following path cannot be queried: relatedPosts.docs

[DanRibbens]

The join field doesn't support querying yet. We should mention this in the docs until this can be added. For now you will need to first query the related collection and use the relationship IDs from the first query like this:

``
const posts = await payload.find({
collection: 'posts',
depth: 0,
limit: 0,
paginaction: false
where: {
category: { exists: true }
},
select: { category: true }
})

const categoriesHavingPosts = await payload.find({
collection: 'categories',
where: {
id: { in: posts.map(({ category }) => category ) }
}
})

I want to be able to support this in one request in the future.

[daohall]

I see. Got it. Thanks for the clarification

[matthijs166]

Plus one for this feature!

Got also this case for access control.

Suppose we got students assigned to classrooms.
For a certain type of user, they only need to see and edit the rooms that are empty with no students.

Now we need to do a big fetch of every student before even querying the rooms..