In a typical web application, we may often need to make multiple GraphQL queries to fetch data from our server. However, making separate requests for each query can lead to increased latency and performance issues. To overcome this, we can use batched and deferred GraphQL queries, which allow us to combine and delay the execution of multiple queries in a single request.

What are Batched and Deferred GraphQL Queries?

• Batched Queries: Batched queries involve sending multiple GraphQL queries in a single request payload. The server processes these queries together and returns a corresponding response that contains results for each query in the batch.

• Deferred Queries: Deferred queries allow us to specify which parts of the query should be executed later, including waiting for other operations to complete or be resolved first. This way, we can defer the execution of certain parts of the query until they are needed, thus optimizing the data retrieval process.

Implementing Batched and Deferred Queries

To implement batched and deferred GraphQL queries in Javascript, we can make use of popular GraphQL client libraries, such as Apollo Client or Relay.

Apollo Client

Apollo Client is a powerful GraphQL client library that provides excellent support for batched and deferred queries. Here’s an example of how we can use Apollo Client to implement batched and deferred queries:

import { ApolloClient, InMemoryCache, gql } from '@apollo/client';

const client = new ApolloClient({
  uri: 'https://api.example.com/graphql',
  cache: new InMemoryCache(),
});

const query1 = gql`
  query Query1 {
    // Query1 definition...
  }
`;

const query2 = gql`
  query Query2 {
    // Query2 definition...
  }
`;

Promise.all([client.query({ query: query1 }), client.query({ query: query2 })])
  .then(([query1Result, query2Result]) => {
    // Handle individual query results...
  })
  .catch((error) => {
    // Handle error...
  });

In the above example, we create an Apollo Client instance and configure it with the GraphQL server URL and an in-memory cache. Then, we define two GraphQL queries (query1 and query2) using the gql template literal function.

We pass an array of promises to Promise.all, where each promise represents a separate query execution using the Apollo Client’s query method. Finally, we handle the results or errors of each individual query using then and catch respectively.

Relay

Relay is another popular GraphQL client library that supports batched and deferred queries. Let’s see how we can use Relay to achieve the same:

import { Environment, Network, RecordSource, Store } from 'relay-runtime';

const fetchQuery = async (operation, variables) => {
  const response = await fetch('https://api.example.com/graphql', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      query: operation.text,
      variables,
    }),
  });

  return await response.json();
};

const createEnvironment = () => {
  const network = Network.create(fetchQuery);
  const store = new Store(new RecordSource());

  return new Environment({
    network,
    store,
  });
};

const environment = createEnvironment();

const query1 = gql`
  query Query1 {
    // Query1 definition...
  }
`;

const query2 = gql`
  query Query2 {
    // Query2 definition...
  }
`;

const executeQueries = async () => {
  const operation1 = createOperationDescriptor(query1, {});
  const operation2 = createOperationDescriptor(query2, {});

  await environment.execute({
    operation: operation1,
    // Specify deferred and other options here...
  });

  await environment.execute({
    operation: operation2,
    // Specify deferred and other options here...
  });

  // Access query results using environment.getStore().getSource(), etc.
};

executeQueries();

In the above example, we define a fetchQuery function that handles the HTTP request to the GraphQL server. We then create an instance of the Relay Environment, which connects the network and data store.

We define two GraphQL queries (query1 and query2) using the gql template literal function. Within the executeQueries function, we create operation descriptors for each query and execute them using the Relay Environment’s execute method.

Conclusion

Batched and deferred queries in GraphQL can significantly improve the performance of our web applications by reducing the number of round trips to the server and optimizing the data retrieval process. In this article, we explored how to implement batched and deferred queries using popular JavaScript GraphQL client libraries like Apollo Client and Relay. By implementing these techniques, we can ensure efficient utilization of network resources and enhance the user experience. #GraphQL #JavaScript