Implementing pagination in vanilla GraphQL

Pagination in vanilla GraphQL

// Pagination argument type to represent offset and limit argumentsconst PaginationArgType = new GraphQLInputObjectType({  name: 'PaginationArg',  fields: {    offset: {      type: GraphQLInt,      description: "Skip n rows."    },    first: {      type: GraphQLInt,      description: "First n rows after the offset."    },  }})// Function to generate paginated list type for a GraphQLObjectType (for representing paginated response)// Accepts a GraphQLObjectType as an argument and gives a paginated list type to represent paginated response.const PaginatedListType = (ItemType) => new GraphQLObjectType({  name: 'Paginated' + ItemType, // So that a new type name is generated for each item type, when we want paginated types for different types (eg. for Person, Book, etc.). Otherwise, GraphQL would complain saying that duplicate type is created when there are multiple paginated types.  fields: {    count: { type: GraphQLInt },    items: { type: new GraphQLList(ItemType) }  }})// Type for representing a single item. eg. Personconst PersonType = new GraphQLObjectType({  name: 'Person',  fields: {    id: { type: new GraphQLNonNull(GraphQLID) },    name: { type: GraphQLString },  }})// Query type which accepts pagination arguments with resolve functionconst PersonQueryTypes = {  people: {    type: PaginatedListType(PersonType),    args: {       pagination: {         type: PaginationArgType,         defaultValue: { offset: 0, first: 10 }       },    },    resolve: (_, args) => {      const { offset, first } = args.pagination      // Call MongoDB/Mongoose functions to fetch data and count from database here.      return {        items: People.find().skip(offset).limit(first).exec()        count: People.count()      }    },  }}// Root query typeconst QueryType = new GraphQLObjectType({  name: 'QueryType',  fields: {    ...PersonQueryTypes,  },});// GraphQL Schemaconst Schema = new GraphQLSchema({  query: QueryType});

and when querying:

{  people(pagination: {offset: 0, first: 10}) {    items {      id      name    }    count  }}

Have created a launchpad here.

There's a number of ways you could implement pagination, but here's two simple example resolvers that use Mongoose to get you started:

Simple pagination using limit and skip:

(obj, { pageSize = 10, page = 0 }) => {  return Foo.find()    .skip(page*pageSize)    .limit(pageSize)    .exec()}

Using _id as a cursor:

(obj, { pageSize = 10, cursor }) => {  const params = cursor ? {'_id': {'$gt': cursor}} : undefined  return Foo.find(params).limit(pageSize).exec()}