Relationship Field

The Relationship field is one of the most powerful fields Payload features. It provides for the ability to easily relate documents together.

Example uses:

To add Product documents to an Order document
To allow for an Order to feature a placedBy relationship to either an Organization or User collection
To assign Category documents to Post documents

Config

Option	Description
`name` *	To be used as the property name when stored and retrieved from the database.
`relationTo` *	Provide one or many collection `slug`s to be able to assign relationships to.
`hasMany`	Boolean when, if set to `true`, allows this field to have many relations instead of only one.
`maxDepth`	Sets a number limit on iterations of related documents to populate when queried. Depth
`label`	Used as a field label in the Admin panel and to name the generated GraphQL type.
`unique`	Enforce that each entry in the Collection has a unique value for this field.
`validate`	Provide a custom validation function that will be executed on both the Admin panel and the backend. More
`index`	Build a MongoDB index for this field to produce faster queries. Set this field to `true` if your users will perform queries on this field's data often.
`saveToJWT`	If this field is top-level and nested in a config supporting Authentication, include its data in the user JWT.
`hooks`	Provide field-based hooks to control logic for this field. More
`access`	Provide field-based access control to denote what users can see and do with this field's data. More
`hidden`	Restrict this field's visibility from all APIs entirely. Will still be saved to the database, but will not appear in any API or the Admin panel.
`defaultValue`	Provide data to be used for this field's default value.
`localized`	Enable localization for this field. Requires localization to be enabled in the Base config.
`required`	Require this field to have a value.
`admin`	Admin-specific configuration. See the default field admin config for more details.

* An asterisk denotes that a property is required.

Tip:
The Depth parameter can be used to automatically populate related documents that are returned by the API.

How the data is saved

Given the variety of options possible within the relationship field type, the shape of the data needed for creating and updating these fields can vary. The following sections will describe the variety of data shapes that can arise from this field.

Has One

The most simple pattern of a relationship is to use hasMany: false with a relationTo that allows for only one type of collection.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owner', // required
      type: 'relationship', // required
      relationTo: 'users', // required
      hasMany: false,
    }
  ]
}

The shape of the data to save for a document with the field configured this way would be:

  {
     // Mongo ObjectID of the related user
    "owner": "6031ac9e1289176380734024"
  }

When querying documents in this collection via REST API, you could query as follows:

?where[owner][equals]=6031ac9e1289176380734024.

Has One - Polymorphic

Also known as dynamic references, in this configuration, the relationTo field is an array of Collection slugs that tells Payload which Collections are valid to reference.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owner', // required
      type: 'relationship', // required
      relationTo: ['users', 'organizations'], // required
      hasMany: false,
    }
  ]
}

The shape of the data to save for a document with more than one relationship type would be:

  {
    "owner": {
      "relationTo": "organizations",
      "value": "6031ac9e1289176380734024"
    }
  }

Here is an example for how to query documents by this data (note the difference in referencing the owner.value):

?where[owner.value][equals]=6031ac9e1289176380734024.

You can also query for documents where a field has a relationship to a specific Collection:

?where[owners.relationTo][equals]=organizations.

This query would return only documents that have an owner relationship to organizations.

Has Many

The hasMany tells Payload that there may be more than one collection saved to the field.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owners', // required
      type: 'relationship', // required
      relationTo: 'users', // required
      hasMany: true,
    }
  ]
}

To save the to hasMany relationship field we need to send an array of IDs:

  {
    "owners": [ "6031ac9e1289176380734024", "602c3c327b811235943ee12b" ]
  }

When querying documents, the format does not change for arrays:

?where[owners][equals]=6031ac9e1289176380734024.

Has Many - Polymorphic

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owners', // required
      type: 'relationship', // required
      relationTo: ['users', 'organizations'], // required
      hasMany: true,
      required: true,
    }
  ]
}

Relationship fields with hasMany set to more than one kind of collections save their data as an array of objects—each containing the Collection slug as the relationTo value, and the related document id for the value:

{
  "owners": [
    {
      "relationTo": "users",
      "value": "6031ac9e1289176380734024"
    }, {
      "relationTo": "organizations",
      "value": "602c3c327b811235943ee12b"
    }
  ]
}

Querying is done in the same way as the earlier Polymorphic example:

?where[owners.value][equals]=6031ac9e1289176380734024.