GraphQL terminology

The GitHub GraphQL API represents an architectural and conceptual shift from the GitHub REST API. You will likely encounter some new terminology in the GraphQL APIreference docs.

Schema

A schema defines a GraphQL API's type system. It describes the complete set of possible data (objects, fields, relationships, everything) that a client can access. Calls from the client arevalidated andexecuted against the schema. A client can find information about the schema viaintrospection. A schema resides on the GraphQL API server. For more information, seeDiscovering the GraphQL API.

Field

A field is a unit of data you can retrieve from an object. As theofficial GraphQL docs say:"The GraphQL query language is basically about selecting fields on objects."

Theofficial spec also says about fields:

All GraphQL operations must specify their selections down to fields which return scalar values to ensure an unambiguously shaped response.

This means that if you try to return a field that is not a scalar, schema validation will throw an error. You must add nested subfields until all fields return scalars.

Argument

An argument is a set of key-value pairs attached to a specific field. Some fields require an argument.Mutations require an input object as an argument.

Implementation

A GraphQL schema may use the termimplements to define how an object inherits from aninterface.

Here's a contrived example of a schema that defines interfaceX and objectY:

interface X{some_field: String!other_field: String!}type Y implements X{some_field: String!other_field: String!new_field: String!}

This means objectY requires the same fields/arguments/return types that interfaceX does, while adding new fields specific to objectY. (The! means the field is required.)

In the reference docs, you'll find that:

• Eachobject lists the interface(s)from which it inherits underImplements.

• Eachinterface lists the objectsthat inherit from it underImplementations.

Connection

Connections let you query related objects as part of the same call. With connections, you can use a single GraphQL call where you would have to use multiple calls to a REST API. For more information, seeMigrating from REST to GraphQL.

It's helpful to picture a graph: dots connected by lines. The dots are nodes, the lines are edges. A connection defines a relationship between nodes.

Edge

Edges represent connections between nodes. When you query a connection, you traverse its edges to get to its nodes. Everyedges field has anode field and acursor field. Cursors are used for pagination. For more information, seeUsing pagination in the GraphQL API.

Node

Node is a generic term for an object. You can look up a node directly, or you can access related nodes via a connection. If you specify anode that does not return ascalar, you must include subfields until all fields return scalars. For information on accessing node IDs via the REST API and using them in GraphQL queries, seeUsing global node IDs.

Discovering the GraphQL API

GraphQL isintrospective. This means you can query a GraphQL schema for details about itself.

• Query__schema to list all types defined in the schema and get details about each:

  query{  __schema{    types{      name      kind      description      fields{        name}}}}

• Query__type to get details about any type:

  query{  __type(name:"Repository"){    name    kind    description    fields{      name}}}

• You can also run anintrospection query of the schema via aGET request:

  curl -H "Authorization: bearer TOKEN" https://api.github.com/graphql

  Note

  If you get the response"message": "Bad credentials" or401 Unauthorized, check that you are using a valid token. If you receive a403 error withResource not accessible by personal access token, ensure that your fine-grained personal access token is targeted to the correct resource owner. For example, it must target the organization that owns the repository you are trying to access.

  The results are in JSON, so we recommend pretty-printing them for easier reading and searching. You can use a command-line tool likejq or pipe the results intopython -m json.tool for this purpose.

  Alternatively, you can pass theidl media type to return the results in IDL format, which is a condensed version of the schema:

  $curl -H"Authorization: bearer TOKEN" -H"Accept: application/vnd.github.v4.idl" \https://api.github.com/graphql

  Note

  The introspection query is probably the onlyGET request you'll run in GraphQL. If you're passing a body, the GraphQL request method isPOST, whether it's a query or a mutation.

  For more information about performing queries, seeForming calls with GraphQL.