GraphQL Cursor Connections Specification

This specification aims to provide an option for GraphQL clients to consistently handle pagination best practices with support for related metadata via a GraphQL server. This spec proposes calling this pattern "Connections" and exposing them in a standardized way.

In the query, the connection model provides a standard mechanism for slicing and paginating the result set.

In the response, the connection model provides a standard way of providing cursors, and a way of telling the client when more results are available.

An example of all four of those is the following query:

{
  user {
    id
    name
    friends(first: 10, after: "opaqueCursor") {
      edges {
        cursor
        node {
          id
          name
        }
      }
      pageInfo {
        hasNextPage
      }
    }
  }
}

In this case, friends is a connection. That query demonstrates the four features described above:

• Slicing is done with the first argument to friends. This asks for the connection to return 10 friends.
• Pagination is done with the after argument to friends. We passed in a cursor, so we asked for the server to return friends after that cursor.
• For each edge in the connection, we asked for a cursor. This cursor is an opaque string, and is precisely what we would pass to the after arg to paginate starting after this edge.
• We asked for hasNextPage; that will tell us if there are more edges available, or if we've reached the end of this connection.

This section of the spec describes the formal requirements around connections.

Reserved Types

A GraphQL server which conforms to this spec must reserve certain types and type names to support the pagination model of connections. In particular, this spec creates guidelines for the following types:

• Any object whose name ends in "Connection".
• An object named PageInfo.

Connection Types

Any type whose name ends in "Connection" is considered by this spec to be a Connection Type. Connection types must be an "Object" as defined in the "Type System" section of the GraphQL Specification.

Fields

Connection types must have fields named edges and pageInfo. They may have additional fields related to the connection, as the schema designer sees fit.

Edges

A "Connection Type" must contain a field called edges. This field must return a list type that wraps an edge type, where the requirements of an edge type are defined in the "Edge Types" section below.

PageInfo

A "Connection Type" must contain a field called pageInfo. This field must return a non-null PageInfo object, as defined in the "PageInfo" section below.

Introspection

If ExampleConnection existed in the type system, it would be a connection, since its name ends in "Connection". If this connection's edge type was named ExampleEdge, then a server that correctly implements the above requirement would accept the following introspection query, and return the provided response:

{
  __type(name: "ExampleConnection") {
    fields {
      name
      type {
        name
        kind
        ofType {
          name
          kind
        }
      }
    }
  }
}

returns

{
  "data": {
    "__type": {
      "fields": [
        // May contain other items
        {
          "name": "pageInfo",
          "type": {
            "name": null,
            "kind": "NON_NULL",
            "ofType": {
              "name": "PageInfo",
              "kind": "OBJECT"
            }
          }
        },
        {
          "name": "edges",
          "type": {
            "name": null,
            "kind": "LIST",
            "ofType": {
              "name": "ExampleEdge",
              "kind": "OBJECT"
            }
          }
        }
      ]
    }
  }
}

Edge Types

A type that is returned in list form by a connection type's edges field is considered by this spec to be an Edge Type. Edge types must be an "Object" as defined in the "Type System" section of the GraphQL Specification.

Fields

Edge types must have fields named node and cursor. They may have additional fields related to the edge, as the schema designer sees fit.

Node

An "Edge Type" must contain a field called node. This field must return either a Scalar, Enum, Object, Interface, Union, or a Non-Null wrapper around one of those types. Notably, this field cannot return a list.

NOTE The naming echoes that of the "Node" interface and "node" root field as described in a later section of this spec. Spec-compliant clients can perform certain optimizations if this field returns an object that implements Node, however, this is not a strict requirement for conforming.

Cursor

An "Edge Type" must contain a field called cursor. This field must return a type that serializes as a String; this may be a String, a Non-Null wrapper around a String, a custom scalar that serializes as a String, or a Non-Null wrapper around a custom scalar that serializes as a String.

Whatever type this field returns will be referred to as the cursor type in the rest of this spec.

The result of this field should be considered opaque by the client, but will be passed back to the server as described in the "Arguments" section below.

Introspection

If ExampleEdge is an edge type in our schema, that returned "Example" objects, then a server that correctly implements the above requirement would accept the following introspection query, and return the provided response:

{
  __type(name: "ExampleEdge") {
    fields {
      name
      type {
        name
        kind
        ofType {
          name
          kind
        }
      }
    }
  }
}

returns

{
  "data": {
    "__type": {
      "fields": [
        // May contain other items
        {
          "name": "node",
          "type": {
            "name": "Example",
            "kind": "OBJECT",
            "ofType": null
          }
        },
        {
          "name": "cursor",
          "type": {
            // This shows the cursor type as String!, other types are possible
            "name": null,
            "kind": "NON_NULL",
            "ofType": {
              "name": "String",
              "kind": "SCALAR"
            }
          }
        }
      ]
    }
  }
}

Arguments

A field that returns a Connection Type must include forward pagination arguments, backward pagination arguments, or both. These pagination arguments allow the client to slice the set of edges before it is returned.

Forward pagination arguments

To enable forward pagination, two arguments are required.

• first takes a non-negative integer.
• after takes the cursor type as described in the cursor field section.

The server should use those two arguments to modify the edges returned by the connection, returning edges after the after cursor, and returning at most first edges.

You should generally pass the cursor of the last edge in the previous page for after.

Backward pagination arguments

To enable backward pagination, two arguments are required.

• last takes a non-negative integer.
• before takes the cursor type as described in the cursor field section.

The server should use those two arguments to modify the edges returned by the connection, returning edges before the before cursor, and returning at most last edges.

You should generally pass the cursor of the first edge in the next page for before.

Edge order

You may order the edges however your business logic dictates, and may determine the ordering based upon additional arguments not covered by this specification. But the ordering must be consistent from page to page, and importantly, The ordering of edges should be the same when using first/after as when using last/before, all other arguments being equal. It should not be reversed when using last/before. More formally:

• When before: cursor is used, the edge closest to cursor must come last in the result edges.
• When after: cursor is used, the edge closest to cursor must come first in the result edges.

Pagination algorithm

To determine what edges to return, the connection evaluates the before and after cursors to filter the edges, then evaluates first to slice the edges, then last to slice the edges.

NOTE Including a value for both first and last is strongly discouraged, as it is likely to lead to confusing queries and results. The PageInfo section goes into more detail here.

More formally:

EdgesToReturn(allEdges, before, after, first, last):

• Let {edges} be the result of calling {ApplyCursorsToEdges(allEdges, before, after)}.
• If {first} is set:
  • If {first} is less than 0:
    • Throw an error.
  • If {edges} has length greater than {first}:
    • Slice {edges} to be of length {first} by removing edges from the end of {edges}.
• If {last} is set:
  • If {last} is less than 0:
    • Throw an error.
  • If {edges} has length greater than {last}:
    • Slice {edges} to be of length {last} by removing edges from the start of {edges}.
• Return {edges}.

ApplyCursorsToEdges(allEdges, before, after):

• Initialize {edges} to be {allEdges}.
• If {after} is set:
  • Let {afterEdge} be the edge in {edges} whose {cursor} is equal to the {after} argument.
  • If {afterEdge} exists:
    • Remove all elements of {edges} before and including {afterEdge}.
• If {before} is set:
  • Let {beforeEdge} be the edge in {edges} whose {cursor} is equal to the {before} argument.
  • If {beforeEdge} exists:
    • Remove all elements of {edges} after and including {beforeEdge}.
• Return {edges}.

PageInfo

The server must provide a type called PageInfo.

Fields

PageInfo must contain fields hasPreviousPage and hasNextPage, both of which return non-null booleans. It must also contain fields startCursor and endCursor, both of which return opaque strings. The fields startCursor and endCursor can be null if there are no results.

hasPreviousPage is used to indicate whether more edges exist prior to the set defined by the clients arguments. If the client is paginating with last/before, then the server must return {true} if prior edges exist, otherwise {false}. If the client is paginating with first/after, then the client may return {true} if edges prior to after exist, if it can do so efficiently, otherwise may return {false}. More formally:

HasPreviousPage(allEdges, before, after, first, last):

• If {last} is set:
  • Let {edges} be the result of calling {ApplyCursorsToEdges(allEdges, before, after)}.
  • If {edges} contains more than {last} elements return {true}, otherwise {false}.
• If {after} is set:
  • If the server can efficiently determine that elements exist prior to {after}, return {true}.
• Return {false}.

hasNextPage is used to indicate whether more edges exist following the set defined by the clients arguments. If the client is paginating with first/after, then the server must return {true} if further edges exist, otherwise {false}. If the client is paginating with last/before, then the client may return {true} if edges further from before exist, if it can do so efficiently, otherwise may return {false}. More formally:

HasNextPage(allEdges, before, after, first, last):

• If {first} is set:
  • Let {edges} be the result of calling {ApplyCursorsToEdges(allEdges, before, after)}.
  • If {edges} contains more than {first} elements return {true}, otherwise {false}.
• If {before} is set:
  • If the server can efficiently determine that elements exist following {before}, return {true}.
• Return {false}.

NOTE When both first and last are included, both of the fields should be set according to the above algorithms, but their meaning as it relates to pagination becomes unclear. This is among the reasons that pagination with both first and last is discouraged.

startCursor and endCursor must be the cursors corresponding to the first and last nodes in edges, respectively.

NOTE As this spec was created with Relay Classic in mind, it's worth noting that Relay Legacy did not define startCursor and endCursor, and relied on selecting the cursor of each edge; Relay Modern began selecting startCursor and endCursor instead to save bandwidth (since it doesn't use any cursors in between).

Introspection

A server that correctly implements the above requirement would accept the following introspection query, and return the provided response:

{
  __type(name: "PageInfo") {
    fields {
      name
      type {
        name
        kind
        ofType {
          name
          kind
        }
      }
    }
  }
}

returns

{
  "data": {
    "__type": {
      "fields": [
        // May contain other fields.
        {
          "name": "hasNextPage",
          "type": {
            "name": null,
            "kind": "NON_NULL",
            "ofType": {
              "name": "Boolean",
              "kind": "SCALAR"
            }
          }
        },
        {
          "name": "hasPreviousPage",
          "type": {
            "name": null,
            "kind": "NON_NULL",
            "ofType": {
              "name": "Boolean",
              "kind": "SCALAR"
            }
          }
        },
        {
          "name": "startCursor",
          "type": {
            "name": "String",
            "kind": "SCALAR",
            "ofType": null
          }
        },
        {
          "name": "endCursor",
          "type": {
            "name": "String",
            "kind": "SCALAR",
            "ofType": null
          }
        }
      ]
    }
  }
}