What causes "Not supported" in payloadcms/payload?

Avoid deep-path queries through polymorphic (`collection: [...]`) join fields; restructure the query to filter on the target collections directly.

payloadcms/payload · error · APIError

Not supported

Error message

Not supported

What it means

`APIError('Not supported')` from the `join` field case in `getTableColumnFromPath`: the code path that turns a join field into a SQL join rejects polymorphic joins, i.e. when `field.collection` is an array (the join points to one of several collections selectable per row). The Drizzle query builder does not implement cross-collection polymorphic joins for this traversal, so it refuses rather than produce wrong SQL.

Source

Thrown at packages/drizzle/src/queries/getTableColumnFromPath.ts:369

          constraintPath: `${constraintPath}${field.name}.`,
          constraints,
          fields: field.flattenedFields,
          joins,
          locale,
          parentIsLocalized: parentIsLocalized || field.localized,
          pathSegments: pathSegments.slice(1),
          rootTableName,
          selectFields,
          selectLocale,
          tableName: newTableName,
          tableNameSuffix: `${tableNameSuffix}${toSnakeCase(field.name)}_`,
          value,
        })
      }

      case 'join': {
        if (Array.isArray(field.collection)) {
          throw new APIError('Not supported')
        }

        const newCollectionPath = pathSegments.slice(1).join('.')

        if (field.hasMany) {
          const relationTableName = `${adapter.tableNameMap.get(toSnakeCase(field.collection))}${adapter.relationshipsSuffix}`

          const existingTable = joins.find(
            (e) => e.queryPath === `${constraintPath}${field.name}._rels`,
          )

          const aliasRelationshipTable = (existingTable?.table ??
            getTableAlias({
              adapter,
              tableName: relationTableName,
            }).newAliasTable) as PgTableWithColumns<any>

          const relationshipField = getFieldByPath({

View on GitHub (pinned to 00c58b35c0)

Solutions

Avoid deep-path queries through polymorphic (`collection: [...]`) join fields; restructure the query to filter on the target collections directly.
If you control the schema, narrow the join field to a single `collection` so a concrete join is possible.
Perform the filter in application logic by fetching and post-filtering.

Example fix

// before: join field 'related' allows ['posts','pages']
await payload.find({ collection: 'sections', where: { 'related.title': { contains: 'x' } } })
// after: query each target collection, or restrict the join to one collection
//   join: { name: 'related', collection: 'posts' }

Defensive patterns

Strategy: validation

Validate before calling

// Avoid deep-path queries through polymorphic join fields
function isPolymorphicJoin(field) {
  return field?.type === 'join' && Array.isArray(field.collection)
}
const targetField = payload.collections[collection].config.flattenedFields[seg]
if (isPolymorphicJoin(targetField)) {
  throw new Error(`Cannot query through polymorphic join '${seg}'; query target collections directly.`)
}

Type guard

const isPolymorphicJoinField = (f): boolean => f?.type === 'join' && Array.isArray(f?.collection)

Try / catch

try {
  await payload.find({ collection, where })
} catch (err) {
  if (err?.statusCode === 400 && err?.message === 'Not supported') {
    return res.status(400).json({ error: 'Querying this polymorphic join path is not supported.' })
  }
  throw err
}

Prevention

Restrict join fields to a single collection when deep filtering is required.
Filter target collections directly instead of traversing polymorphic joins.
Validate API query input against the field schema before issuing the query.

When it happens

Trigger: Querying (`where` or `select`) through a join-type field whose `collection` is an array of allowed collections, e.g. a blocks/join field that can reference multiple collections, by a path that requires traversing the join.

Common situations: A `join` field configured with multiple target collections; querying a polymorphic relationship/join by a deep path; a UI or API query autogenerated for a polymorphic join field.

Related errors

AI-assisted analysis of payloadcms/payload@00c58b35c0 (2026-08-12). Data as JSON: /api/errors/687b9fb7b6f73474. Report an issue: GitHub.