GraphQL in Action

7 Optimizing data fetching

This chapter covers

• Caching and batching data-fetch operations
• Using the DataLoader library with primary keys and custom IDs
• Using GraphQL’s union type and field arguments
• Reading data from MongoDB

Now that we have a GraphQL service with a multimodel schema, we can look at one of GraphQL’s most famous problems, the N+1 queries problem. We ended the previous chapter with a GraphQL query that fetches data from three database tables.

Listing 7.1 The N+1 query example

{
  taskMainList {
    // ·-·-·
    author {
      // ·-·-·
    }
    approachList {
      // ·-·-·
      author {
        // ·-·-·
      }
    }
  }
}

Because the GraphQL runtime traverses the tree field by field and resolves each field on its own as it does, this simple GraphQL query resulted in a lot more ...