Limit M2M items to max 2 per parent via Flows (Directus 11.7.2) – running into skeleton‑row + mis‑count issues

Help
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1

Hi everyone :waving_hand:

I’m stuck on something that feels simple, but I haven’t found a clean solution and would love advice / best‑practice.

1 · Context

Table Fields (relevant)
pytania (questions) id (UUID PK), …
odpowiedzi (answers) id (UUID PK), …
pytania_odpowiedzi (M2M junction) id (AI PK) · pytania_id (FK → questions.id) · odpowiedzi_id (FK → answers.id) · sort

Directus 11.7.2, PostgreSQL 14.

Business rule: question can have at most two answers linked (some sort of quiz).

2 · What I tried (Flows only)

  • Trigger – Filter (Blocking) on items.create (collection = pytania_odpowiedzi)

  • Read Data – count rows with
    { “pytania_id”: { “_eq”: “{{$trigger.payload.pytania_id}}” } }

  • Run Script – if existing > 2 → throw new Error().

3 · Issues I hit

Issue What actually happens
A. skeleton row the M2M UI first sends an INSERT with only id (+ sort) – both FKs are NULL. My filter fires on that step → if I block it, a record with NULLs is left behind; if I let it pass, the later PATCH inserts the FK values and bypasses my limit.
B. no Min/Max in interface I can’t simply tell the field “max items = 2”; that option isn’t available for M2M yet or im blind.

4 · Things I haven’t tried yet

  • Hook (extensions/hooks) – would catch items.update after both FKs are present.
  • SQL constraint / trigger in Postgres – 100 % reliable but moves logic outside Directus.
  • Custom Vue interface to hide the “Add” button after 2 items (would like to avoid that option).

I’m still hoping to keep it no‑code (Flows) if at all possible.

5 · Questions to the community

  1. Has anyone successfully enforced “max N items” in a junction table using only Flows?
    If yes, how did you manage to do that*
  2. Is there a way to make the Read Data filter reliably resolve {{$trigger.payload.pytania_id}} (or maybe use $trigger.keys…) so it never falls back to a full‑table read?
  3. Any news on a built‑in Min/Max setting for relational fields? (I saw feature requests #9445, #19556 but not sure of their status.)

6 · Environment

  • Directus: 11.7.2 (Docker)
  • Database: PostgreSQL 14
  • Auth: local
  • Flows engine enabled, no custom extensions yet.

Any pointers, examples or “don’t bother, use a DB trigger instead” are greatly appreciated!

Thanks :folded_hands: