Is it possible to create segments on OneToMany relationships?

I have a fairly trivial situation that I’m struggling to create a segment for in Forest.

Users can book appointment on our platform and I have a “users” table and a “bookings” table.

I would like to create a segment for “users without bookings” or “users with >1 booking with status ‘accepted’ and type ‘consultation’”, but it seems like that may be impossible with Forest.

From the docs, it looks like filters only support one-to-one and many-to-one relationships (whereas my relationship is one-to-many), and the .addSegment function has to return a Forest admin condition tree.

I’ve tried something like:

  collection.addSegment("No bookings", async (context) => {
    return { field: "booking:status", operator: "Equal", value: "ACCEPTED" }

but this returns Unexpected field type 'OneToMany': 'users.bookings'.

It seems like this usecase should be handled, since it’s trivial to write SQL for this, but I can’t figure it out. Is there some other lower-level way to define a segment?

Note that there are potentially thousands of bookings and thousands of users, so finding all users who have a booking and doing a "user_id" in [list of user ids] is not feasible for us.


  • Project name: outro-backend
  • Team name: outro
  • Environment name: development/staging/prod
  • Agent technology: nodejs (@forestadmin/agent)
  • Database type: Postgres
  • Recent changes made on your end if any: N/A

I’m investigating on this, but we don’t have any other “out of the box” solution for your problem.

What is the volume of records you’re having on these queries?

  • Users with bookings → thousands
  • Users without bookings → ?
  • Users with at least one accepted booking of type consultation → ?

Today our numbers are small, but we expect them to grow quickly.

I imagine it will be 50:50 for users with and without any appointments booked, so with 1000 users who’ve booked an appt, another 1000 will be in the other category.

Users with at least one accepted booking of type “consultation” will also be large numbers since we only have 4 appointment types.

I can probably make our segment sizes smaller or at a max limit and Forest still be usable for us.

Is there some limit you recommend?

I’m also thinking of alternative approaches. Maybe I can create cohorts on PostHog and have those pulled into and matched up with our database. I’m curious whether you have any other strategies for this type of thing.

You’ll have some limit both in terms of performance and what Postgresql will accept to do. I know that there is a limit for list of values with the IN operator.

If you’re able to limit these segments for instance by limiting them to the “X most recent users” or whatever other criterion makes sense for your business, it’ll help a lot for sure.

I was trying to experiment with SQL views also, on my side. It could work but with some other limitations:

  • Using them as intermediate collections with 1-1 relationships & construct the segment with this won’t work because, in the end, the agent will do exactly the same (retrieve the whole list of ids and inject it in a filter).
  • Using them as collections directly will display them as independent collections, without the customizations you could define on your real users collection.

Ideally, having this data written somewhere in your DB would work perfectly in terms of performance and experience.

Do you know what the limit is?

I’m also wondering if it’s possible to create a paged segment, so the the handler only needs to return the list of IDs for a certain page.

I could not find any info about such limit. I based my answer on a past experience with a limitation, but now that I’m thinking deeper, I recall that it was not on Postgresql.