GraphQL Operations Guide

This guide covers best practices for writing GraphQL operations (queries, mutations, subscriptions) as a client developer. Well-written operations are efficient, type-safe, and maintainable.

Operation Basics

Query Structure

query GetUser($id: ID!) {
  user(id: $id) {
    id
    name
    email
  }
}

Mutation Structure

mutation CreatePost($input: CreatePostInput!) {
  createPost(input: $input) {
    id
    title
    createdAt
  }
}

Subscription Structure

subscription OnMessageReceived($channelId: ID!) {
  messageReceived(channelId: $channelId) {
    id
    content
    sender {
      id
      name
    }
  }
}

Quick Reference

Operation Naming

Variable Syntax

# Required variable
query GetUser($id: ID!) { ... }

# Optional variable with default
query ListPosts($first: Int = 20) { ... }

# Multiple variables
query SearchPosts($query: String!, $status: PostStatus, $first: Int = 10) { ... }

Fragment Syntax

# Define fragment
fragment UserBasicInfo on User {
  id
  name
  avatarUrl
}

# Use fragment
query GetUser($id: ID!) {
  user(id: $id) {
    ...UserBasicInfo
    email
  }
}

Directives

query GetUser($id: ID!, $includeEmail: Boolean!) {
  user(id: $id) {
    id
    name
    email @include(if: $includeEmail)
  }
}

query GetPosts($skipDrafts: Boolean!) {
  posts {
    id
    title
    draft @skip(if: $skipDrafts)
  }
}

Key Principles

1. Request Only What You Need

# Good: Specific fields
query GetUserName($id: ID!) {
  user(id: $id) {
    id
    name
  }
}

# Avoid: Over-fetching
query GetUser($id: ID!) {
  user(id: $id) {
    id
    name
    email
    bio
    posts {
      id
      title
      content
      comments {
        id
      }
    }
    followers {
      id
      name
    }
    # ... many unused fields
  }
}

2. Name All Operations

# Good: Named operation
query GetUserPosts($userId: ID!) {
  user(id: $userId) {
    posts {
      id
      title
    }
  }
}

# Avoid: Anonymous operation
query {
  user(id: "123") {
    posts {
      id
      title
    }
  }
}

3. Use Variables, Not Inline Values

# Good: Variables
query GetUser($id: ID!) {
  user(id: $id) {
    id
    name
  }
}

# Avoid: Hardcoded values
query {
  user(id: "123") {
    id
    name
  }
}

4. Colocate Fragments with Components

// UserAvatar.tsx
export const USER_AVATAR_FRAGMENT = gql`
  fragment UserAvatar on User {
    id
    name
    avatarUrl
  }
`;

function UserAvatar({ user }) {
  return <img src={user.avatarUrl} alt={user.name} />;
}

Reference Files

Detailed documentation for specific topics:

• Queries - Query patterns and optimization
• Mutations - Mutation patterns and error handling
• Fragments - Fragment organization and reuse
• Variables - Variable usage and types
• Tooling - Code generation and linting

Ground Rules

• ALWAYS name your operations (no anonymous queries/mutations)
• ALWAYS use variables for dynamic values
• ALWAYS request only the fields you need
• ALWAYS include id field for cacheable types
• NEVER hardcode values in operations
• NEVER duplicate field selections across files
• PREFER fragments for reusable field selections
• PREFER colocating fragments with components
• USE descriptive operation names that reflect purpose
• USE @include/@skip for conditional fields