Using Connections

GraphQL-Ruby ships with a few implementations of the connection pattern that you can use out of the box. They support Ruby Arrays, Mongoid, Sequel, and ActiveRecord.

Additionally, connections allow you to limit the number of items returned with max_page_size and set the default number of items returned with default_page_size.

Make Connection Fields

Use .connection_type to generate a connection type for paginating over objects of a given type:

field :items, Types::ItemType.connection_type, null: false

The generated return type will be called ItemConnection. Since it ends in *Connection, the field(...) will automatically be configured with connection: true. If the connection type’s name doesn’t end in Connection, you have to add that configuration yourself:

# here's a custom type whose name doesn't end in "Connection", so `connection: true` is required:
field :items, Types::ItemConnectionPage, null: false, connection: true

The field will be given some arguments by default: first, last, after, and before.

Opting out of default connection handling

To opt out of GraphQL-Ruby’s default connection handling, add connection: false to the field definition:

- field :items, Types::ItemType.connection_type, null: false
+ field :items, Types::ItemType.connection_type, null: false, connection: false

Then, add any arguments you want (first, last, after, before) and make sure that your resolver returns an object that can fulfill the fields of the configured return type.

Return Collections

With connection fields, you can return collection objects from fields or resolvers:

def items
  object.items # => eg, returns an ActiveRecord Relation
end

The collection object (Array, Mongoid relation, Sequel dataset, ActiveRecord relation) will be automatically paginated with the provided arguments. Cursors will be generated based on the offset of nodes in the collection.

Make Custom Connections

If you want to paginate something that isn’t supported out-of-the-box, you can implement your own pagination wrapper and hook it up to GraphQL-Ruby. Read more in Custom Connections.

Special Cases

Sometimes, you have one collection that needs special handling, unlike other instances of its class. For cases like this, you can manually apply the connection wrapper in the resolver. For example:

def items
  # Get the ActiveRecord relation to paginate
  relation = object.items
  # Apply a custom wrapper
  Connections::ItemsConnection.new(relation)
end

This way, you can handle this particular relation with custom code.

Max Page Size

You can apply max_page_size to limit the number of items returned and queried from the database, regardless of what the client requests.

• For the whole schema, you can add it to your schema definition:

class MyAppSchema < GraphQL::Schema
  default_max_page_size 50
end

At runtime, that value will be applied to every connection, unless an override is provided as described below.

• For a given field, add it to the field definition with a keyword:

field :items, Item.connection_type, null: false,
  max_page_size: 25

• Dynamically, you can add max_page_size: when you apply custom connection wrappers:

def items
  relation = object.items
  Connections::ItemsConnection.new(relation, max_page_size: 10)
end

To remove a max_page_size setting, you can pass nil. That will allow unbounded collections to be returned to clients.

Default Page Size

You can apply default_page_size to limit the number of items returned and queried from the database when no first or last is provided.

• For the whole schema, you can add it to your schema definition:

class MyAppSchema < GraphQL::Schema
  default_page_size 50
end

At runtime, that value will be applied to every connection, unless an override is provided as described below.

• For a given field, add it to the field definition with a keyword:

field :items, Item.connection_type, null: false,
  default_page_size: 25

• Dynamically, you can add default_page_size: when you apply custom connection wrappers:

def items
  relation = object.items
  Connections::ItemsConnection.new(relation, default_page_size: 10)
end

If max_page_size is set and default_page_size is higher than it, the default_page_size will be clamped down to match max_page_size. If both default_page_size and max_page_size are set to nil, unbounded collections will be returned.