Pagination

As GraphQL continues to gain popularity as a powerful API querying language, it's becoming increasingly common to deal with large datasets.

When querying or mutating a collection of items in GraphQL, it's important to implement pagination to manage data retrieval efficiently.

Pagination is the process of fetching results in smaller chunks, reducing the amount of data transferred over the network and improving the overall performance and user experience of GraphQL APIs.

In this article, we'll take an in-depth look at various pagination techniques in GraphQL, including plurals, slicing, edges, end-of-list indicators, counts, and connections. We'll also provide a complete example of implementing GraphQL pagination using these techniques, which works perfectly for fetching data from Hygraph.

Plurals: Making Collections More Readable and Consistent

In GraphQL, using plural field names for collections is common to make the schema more readable and consistent.

For example, instead of using user for a single user object, using users for a collection of users makes the schema more intuitive. Plural field names also align with the conventions used in REST APIs, making it easier for clients to transition between the two.

Here's an example of a GraphQL query that retrieves a collection of users:

query {
  users {
    id
    name
    email
  }
}

In this query, users is the plural field name for the collection of users. The response will contain an array of user objects, each with their respective id, name, and email fields.

Using plural field names for collections in GraphQL can improve the readability and consistency of the schema, making it easier for clients to understand and navigate the API.

Slicing: Limiting the Number of Results

Slicing is a common pagination technique in GraphQL that allows you to limit the number of results returned in a query.

GraphQL provides two arguments, first and last, that can be used to slice a collection of items. The first argument specifies the maximum number of items to be returned from the beginning of the collection, while the last argument specifies the maximum number of items to be returned from the end of the collection.

Here's an example:

query {
  users(first: 10) {
    id
    name
    email
  }
}

In this query, the first argument limits the results to a maximum of 10 users. The response will contain an array of user objects with their respective id, name, and email fields, but no more than 10 users.

Similarly, you can use the last argument to retrieve a specific number of items from the end of the collection:

query {
  users(last: 5) {
    id
    name
    email
  }
}

In this query, the last argument retrieves the last 5 users from the collection.

Edges: Adding Metadata and Cursor-based Pagination

An edge represents an individual item in a connection, containing both the node (i.e., the item itself) and any metadata associated with that item.

Using edges provides several benefits, such as allowing for cursor-based pagination, where clients can request the next or previous page of results using a cursor instead of relying on offsets.

Cursors are opaque strings that represent a specific position in the collection and can be used to fetch results from that position onwards.

Here's an example of how edges can be used in a GraphQL query:

query {
  usersConnection(first: 10) {
    edges {
      cursor
      node {
        id
        name
        email
      }
    }
  }
}

In this query, we have the following:

• edges field contains an array of edge objects, where each edge represents a user object in the collection.
• cursor field contains the cursor associated with that user object, which can be used for pagination.
• node field within each edge object contains the actual user object, with its respective id, name, and email fields.

Using edges and cursors in GraphQL pagination allows for more efficient and flexible retrieval of data, as clients can request specific pages of results without relying on offsets.

End of List Indicators: Navigating Pagination Boundaries

When implementing pagination in GraphQL, it's important to provide clear indicators of the end of the list. This helps clients know when they have reached the boundaries of the available data and can stop making further requests.

GraphQL provides the hasNextPage and hasPreviousPage fields in the pageInfo object, which indicate whether there are more results in the next or previous page, respectively.

These fields can be used to display appropriate UI elements, such as "Load More" or "Previous Page" buttons, to allow clients to navigate through the paginated results.

Here's an example of how the hasNextPage and hasPreviousPage fields can be used in a GraphQL query:

query {
  usersConnection(first: 10) {
    edges {
      cursor
      node {
        id
        name
        email
      }
    }
    pageInfo {
      hasNextPage
      hasPreviousPage
    }
  }
}

In this query, the hasNextPage field indicates whether there are more results beyond the current page of 10 users, and the hasPreviousPage field indicates results in the previous page.

Providing end of list indicators in GraphQL pagination helps clients navigate the paginated results more efficiently and provides a better user experience.

Counts: Retrieving Total Number of Items

In some cases, clients may need to know the total count of items in a collection, even if they do not request all the items at once.

Hygraph provides this information via the aggregate field. To get the total number of items, you can use the count operation inside aggregate.

Here's an example of how the pageSize field can be used in a GraphQL query:

query {
  usersConnection(first: 10) {
    edges {
      cursor
      node {
        id
        name
        email
      }
    }
    pageInfo {
      hasNextPage
      hasPreviousPage
      pageSize
    }
  }
}

In this query, pageSize refers to the number of items returned per page. To retrieve the total number of items in the collection, use the aggregate { count } operation instead.

Including the pageSize field in GraphQL pagination can provide clients with a better understanding of the total count of items in the collection, even if they are not requesting all the items at once.

Connections: Organizing Pagination Results

Connections are a popular pattern in GraphQL pagination that provides a standardized way to organize and paginate collections. Connections typically consist of a list of edges and a pageInfo object, as discussed earlier.

Using connections in GraphQL pagination allows for consistent and organized retrieval of data, making it easier for clients to consume and navigate through paginated results.

Here's an example of how a connection can be used in a GraphQL query:

query {
  usersConnection(first: 10) {
    edges {
      cursor
      node {
        id
        name
        email
      }
    }
    pageInfo {
      hasNextPage
      hasPreviousPage
      pageSize
    }
  }
}

In this query, the usersConnection field represents the connection for the users collection, and the edges field contains an array of edge objects, similar to the previous examples. The pageInfo field contains metadata about the pagination, including hasNextPage, hasPreviousPage, and pageSize fields.

Using connections in GraphQL pagination provides a consistent and organized way to structure and retrieve paginated results, making it easier for clients to work with and navigate large data collections.

Conclusion

When implementing pagination in GraphQL, it's essential to follow best practices, document your approach in the schema, and consider performance and scalability.

With the right implementation, pagination can greatly improve the efficiency and user experience of your GraphQL API, making it a valuable tool for building robust and performant applications.

So, if you're building a GraphQL API and dealing with large datasets, incorporate pagination in your design.