Unlocking Data Potential: Performance of Exposing Data from Two Tables via GraphQL

Exposing Data from Two Tables via GraphQL

Now that we’ve covered the basics of GraphQL, let’s dive into the main topic: exposing data from two tables using GraphQL. Imagine you have two tables, orders and customers, with the following structures:

Your goal is to retrieve the customer’s name and address, along with their order details, using a single GraphQL query. Sound challenging? Fear not, dear reader, for we’ll guide you through the process step-by-step!

Define Your GraphQL Schema

The first step is to define your GraphQL schema, which describes the structure of your data. In this example, we’ll create two types: Order and Customer.

type Order {
  id: ID!
  customer: Customer!
  orderDate: DateTime!
  total: Float!
}

type Customer {
  id: ID!
  name: String!
  email: String!
  address: String!
}

We’ve defined the Order type with an id, customer (a reference to the Customer type), orderDate, and total. The Customer type has an id, name, email, and address.

Resolvers: The Magic Happens Here

Resolvers are functions that retrieve the data for a specific field in your GraphQL schema. In this example, we’ll create resolvers for the customer field in the Order type and the orders field in the Customer type.

const resolvers = {
  Order: {
    customer: (parent, args, context, info) => {
      return context.db.customers.findOne({ where: { id: parent.customer_id } });
    },
  },
  Customer: {
    orders: (parent, args, context, info) => {
      return context.db.orders.findAll({ where: { customer_id: parent.id } });
    },
  },
};

In the customer resolver, we’re using the customer_id from the Order type to retrieve the corresponding customer from the customers table. Similarly, in the orders resolver, we’re using the id from the Customer type to retrieve the customer’s orders from the orders table.

The Query: Putting it All Together

Now that we have our schema and resolvers in place, it’s time to create a GraphQL query that retrieves the customer’s name and address, along with their order details.

query {
  customer(id: 1) {
    name
    address
    orders {
      id
      orderDate
      total
    }
  }
}

In this query, we’re asking for the customer with id equal to 1, along with their name, address, and a list of their orders, including the id, orderDate, and total.

Performance Benefits

So, what are the performance benefits of exposing data from two tables via GraphQL? Let’s break it down:

1. Fewer Requests**: By using a single GraphQL query, we’ve reduced the number of requests from two (one for each table) to one, resulting in fewer network requests and improved performance.
2. Less Data Transferred**: GraphQL only retrieves the required data, reducing the amount of data transferred between the client and server, which leads to faster load times and improved performance.
3. Better Cacheability**: GraphQL enables better cacheability, as the client can cache the response and reuse it when the same query is executed again, reducing the load on the server and improving performance.