Filtering polymorphic hasMany relationship throws `APIError: Not supported` in admin and REST

[atimmer]

Describe the bug

Filtering a polymorphic relationship field with hasMany: true throws APIError: Not supported.

I can reproduce this in a fresh Payload app with a minimal schema:

• users
• persons
• partners
• articles
  • title: text
  • authors: relationship, relationTo: ['persons', 'partners'], hasMany: true

This affects:

• REST queries like where[authors][exists]=true
• Admin list view filters generated by the UI, including:
  • exists
  • polymorphic equals object notation

Reproduction repo

https://github.com/atimmer/payload-polymorphic-hasmany-filter-repro

Versions

• payload: 3.79.0
• @payloadcms/db-postgres: 3.79.0
• PostgreSQL 16

Minimal field config

{
  name: 'authors',
  type: 'relationship',
  relationTo: ['persons', 'partners'],
  hasMany: true,
}

### Link to the code that reproduces this issue

https://github.com/atimmer/payload-polymorphic-hasmany-filter-repro

### Reproduction Steps

## REST reproduction

This request returns `500` instead of returning the matching article:

```bash
curl -i 'http://127.0.0.1:3110/api/articles?where%5Bauthors%5D%5Bexists%5D=true'

Expected: one article.

Actual: 500 Internal Server Error with APIError: Not supported.

Admin reproduction

1. Log in:

   curl -s -c /tmp/payload-repro-cookies.txt \
     -H 'Content-Type: application/json' \
     -d '{"email":"admin@example.com","password":"password"}' \
     http://127.0.0.1:3110/api/users/login

2. Request the admin list page using the exists filter generated by the admin UI:

   curl -i -b /tmp/payload-repro-cookies.txt \
     'http://127.0.0.1:3110/admin/collections/articles?depth=1&limit=10&where%5Bor%5D%5B0%5D%5Band%5D%5B0%5D%5Bauthors%5D%5Bexists%5D=true&page=1'

3. Request the admin list page using the equals filter generated by the admin UI:

   curl -i -b /tmp/payload-repro-cookies.txt \
     'http://127.0.0.1:3110/admin/collections/articles?depth=1&limit=10&where%5Bor%5D%5B0%5D%5Band%5D%5B0%5D%5Bauthors%5D%5Bequals%5D%5B0%5D%5BrelationTo%5D=persons&where%5Bor%5D%5B0%5D%5Band%5D%5B0%5D%5Bauthors%5D%5Bequals%5D%5B0%5D%5Bvalue%5D=1&page=1'

Expected: the list view loads and shows the matching article.

Actual: the server logs APIError: Not supported from @payloadcms/drizzle/dist/queries/getTableColumnFromPath.js.

Which area(s) are affected?

area: core

Environment Info

Node 25.4.0
npm 11.7.0
pnpm 10.17.0
payload 3.79.0
@payloadcms/db-postgres 3.79.0
@payloadcms/drizzle 3.79.0
next 15.4.11
react / react-dom 19.2.1
OS: macOS Darwin arm64, 16 cores, 64 GB RAM

[naaa760]

@atimmer
please check out this PR!