advanced-queries.md

Advanced Queries

• Relational data queries
  • Expand the GraphQL-Schema
  • Implement the resolver functions
  • Execute a GraphQL query
  • Prepare and usage of persistent GraphQL query

Relational data queries

Expand the GraphQL-Schema

# ...
type Item {
  # ...
  email: String
  # Gravatar picture
  picture: Picture
  # ...
}

# Gravatar picture
type Picture {
  link: String
}
# ...

Implement the resolver function

const crypto = require('crypto');

export const resolvers = {
  // ...
  Item: {
    picture: (parent, args, context, info) => {
      const pictureHash = crypto.createHash('md5').update(parent.email).digest('hex');
      return ({
        link: `https://www.gravatar.com/avatar/${pictureHash}`,
      })
    },
  },
  // ...
}

Execute a GraphQL query

subkit request \
  --token eyJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6ImdvQHN1YmtpdC5pbyJ9.-cVh3sNNCqCZZGdS2jwL_u3aJKXZqNippsMSxj15ROk \
  --url http://localhost:8080/graphql \
  --query 'query loadItem {item(id: "mikebild") {id email picture {link}}}'

Persistent GraphQL query

Benefits of persistent queries:

• Whitelisting GraphQL queries to prevent very complex queries
• Save bandwidth, because only the operationName and variables will submitted

How to create and use persistent queries

Create a file in your root directory named as your query operation name with .gql extention (e.g. ./loadItems.gql).

./loadItems.gql

query loadItems($take: Int) {
  items(take: $take) {
    id
    email
  }
}

Run a persistent query using the operation name only.

subkit request -u http://localhost:8080/graphql --operation loadItems --variables '{"take": 10}'