Cursor-based pagination in GraphQL

Introduction

Cursor-based pagination helps you get small parts of a big list step by step. It is faster and avoids missing or repeating items when the list changes.

Showing posts on a social media feed little by little as you scroll.

Loading search results page by page without skipping or repeating items.

Displaying messages in a chat app where new messages arrive often.

Browsing a large product catalog in an online store smoothly.

Fetching user comments on an article in small chunks.

Syntax

GraphQL

query GetItems($first: Int, $after: String) {
  items(first: $first, after: $after) {
    edges {
      cursor
      node {
        id
        name
      }
    }
    pageInfo {
      endCursor
      hasNextPage
    }
  }
}

$first tells how many items to get.

$after is the cursor pointing to where to start fetching next items.

Examples

Get the first 5 items from the list.

GraphQL

query {
  items(first: 5) {
    edges {
      cursor
      node {
        id
        name
      }
    }
    pageInfo {
      endCursor
      hasNextPage
    }
  }
}

Get 5 items after the cursor "YXJyYXljb25uZWN0aW9uOjQ=" (which points to the 5th item).

GraphQL

query {
  items(first: 5, after: "YXJyYXljb25uZWN0aW9uOjQ=") {
    edges {
      cursor
      node {
        id
        name
      }
    }
    pageInfo {
      endCursor
      hasNextPage
    }
  }
}

Sample Program

This query fetches the first 2 items from the list with their cursors and info if more items exist.

GraphQL

query GetFirstTwoItems {
  items(first: 2) {
    edges {
      cursor
      node {
        id
        name
      }
    }
    pageInfo {
      endCursor
      hasNextPage
    }
  }
}

Important Notes

Cursor values are usually encoded strings that point to a specific item position.

Cursor-based pagination is better than offset pagination when data changes often.

Always check hasNextPage to know if more items can be fetched.

Summary

Cursor-based pagination fetches data in small parts using a cursor to mark position.

It helps avoid missing or repeating items when the list changes.

Use first and after arguments to control pagination.

Practice

1. What is the main purpose of cursor-based pagination in GraphQL?

easy

A. To fetch all data at once without limits

B. To sort data alphabetically

C. To fetch data in small parts using a cursor to mark position

D. To delete data from the database

Solution

1. Step 1: Understand pagination purpose

   Pagination is used to split large data into smaller parts for easier handling.

2. Step 2: Identify cursor role

   Cursor marks the position in the data to fetch the next part without overlap or missing items.

3. Final Answer:

   To fetch data in small parts using a cursor to mark position -> Option C

4. Quick Check:

   Cursor-based pagination = fetch data in parts [OK]

Hint: Cursor marks position to fetch next data chunk [OK]

Common Mistakes:

• Thinking pagination fetches all data at once
• Confusing cursor with sorting
• Assuming pagination deletes data

2. Which of the following is the correct way to request the first 5 items after a cursor in GraphQL?

easy

A. { items(fetch: 5, cursor: "cursor123") { edges { node } } }

B. { items(limit: 5, startAfter: "cursor123") { edges { node } } }

C. { items(take: 5, afterCursor: "cursor123") { edges { node } } }

D. { items(first: 5, after: "cursor123") { edges { node } } }

Solution

1. Step 1: Recall GraphQL cursor pagination syntax

   The standard uses first to limit items and after to specify the cursor.

2. Step 2: Match options with correct syntax

   { items(first: 5, after: "cursor123") { edges { node } } } uses first and after correctly; others use incorrect argument names.

3. Final Answer:

   { items(first: 5, after: "cursor123") { edges { node } } } -> Option D

4. Quick Check:

   Use first and after arguments [OK]

Hint: Use first and after arguments for cursor pagination [OK]

Common Mistakes:

• Using limit instead of first
• Using startAfter or afterCursor which are invalid
• Confusing argument names

3. Given this GraphQL query:
{ users(first: 3, after: "YXJyYXljb25uZWN0aW9uOjE=") { edges { node { id name } } pageInfo { hasNextPage endCursor } } }
What does the endCursor represent in the result?

medium

A. The cursor of the last item in the current page

B. The total number of items in the database

C. The cursor of the first item in the current page

D. The number of pages available

Solution

1. Step 1: Understand pageInfo fields

   endCursor marks the cursor of the last item returned in the current page.

2. Step 2: Differentiate from other fields

   hasNextPage shows if more pages exist; endCursor is not a count or first item cursor.

3. Final Answer:

   The cursor of the last item in the current page -> Option A

4. Quick Check:

   endCursor = last item cursor [OK]

Hint: endCursor points to last item fetched [OK]

Common Mistakes:

• Confusing endCursor with total count
• Thinking endCursor is first item cursor
• Assuming endCursor is page count

4. You wrote this GraphQL query for cursor pagination:
{ posts(first: 10, afterCursor: "abc123") { edges { node { title } } } }
Why does this query fail?

medium

A. The argument should be named after, not afterCursor

B. The first argument must be a string, not a number

C. The edges field is invalid in cursor pagination

D. The cursor value cannot be a string

Solution

1. Step 1: Check argument names for cursor pagination

   The correct argument to specify the cursor is after, not afterCursor.

2. Step 2: Validate other parts

   first accepts a number; edges is valid; cursor values are strings.

3. Final Answer:

   The argument should be named after, not afterCursor -> Option A

4. Quick Check:

   Use 'after' argument name [OK]

Hint: Use 'after' not 'afterCursor' for cursor argument [OK]

Common Mistakes:

• Using incorrect argument names
• Thinking first must be string
• Misunderstanding edges field usage

5. You want to fetch all comments in batches of 4 using cursor-based pagination. The first query is:
{ comments(first: 4) { edges { node { id text } } pageInfo { hasNextPage endCursor } } }
To fetch the next batch, which query should you use?

hard

A. { comments(limit: 4, after: "endCursor_value") { edges { node { id text } } } }

B. { comments(first: 4, after: "endCursor_value") { edges { node { id text } } pageInfo { hasNextPage endCursor } } }

C. { comments(last: 4, after: "endCursor_value") { edges { node { id text } } } }

D. { comments(first: 4, before: "endCursor_value") { edges { node { id text } } } }

Solution

1. Step 1: Understand how to continue pagination

   Use the after argument with the endCursor value from the previous page to fetch the next batch.

2. Step 2: Check argument correctness

   first: 4 limits to 4 items; after moves cursor forward; before or last are for backward pagination.

3. Final Answer:

   { comments(first: 4, after: "endCursor_value") { edges { node { id text } } pageInfo { hasNextPage endCursor } } } -> Option B

4. Quick Check:

   Use first and after with endCursor for next batch [OK]

Hint: Use first and after with endCursor to paginate forward [OK]

Common Mistakes:

• Using before instead of after for next page
• Using last instead of first for forward pagination
• Using limit instead of first argument