GraphQL Pagination: Cursor-based vs. Offset-based
When dealing with large datasets in GraphQL APIs, efficient pagination is crucial for performance and user experience. This module explores two primary strategies: offset-based and cursor-based pagination, highlighting their differences, advantages, and disadvantages.
Understanding Offset-Based Pagination
Offset-based pagination is a common approach where you specify how many items to skip (the offset) and how many items to return (the limit or size). For example, to get the second page of 10 items, you might request items from offset 10 to 20.
Offset-based pagination uses numerical offsets to skip records.
This method is intuitive and easy to implement for simple lists. You tell the server to skip a certain number of records and then return a specified number of records.
The typical implementation involves arguments like offset and limit (or first/after for the number of items). For instance, a query might look like items(offset: 20, limit: 10). While straightforward, it can become inefficient with large offsets as the database might still need to scan through all the skipped records.
Understanding Cursor-Based Pagination
Cursor-based pagination, often referred to as 'keyset pagination' or 'seek pagination', uses opaque cursors to identify the position in a dataset. Instead of skipping a number of items, you request items after a specific cursor.
Cursor-based pagination uses opaque identifiers to navigate through data.
This method is generally more performant and reliable, especially for large or frequently changing datasets. It relies on unique, stable identifiers (cursors) that point to the exact position between items.
In GraphQL, this is commonly implemented using first (number of items to return) and after (the cursor of the last item from the previous page). The cursor itself is usually an encoded string representing the primary key or a combination of fields that uniquely identify an item and its position. This avoids the performance issues associated with large offsets because the database can efficiently seek to the cursor's position.
Comparison: Offset vs. Cursor
| Feature | Offset-Based | Cursor-Based |
|---|---|---|
| Navigation | Numerical offset (skip N items) | Opaque cursor (item after this cursor) |
| Performance | Can degrade with large offsets | Generally consistent, efficient seeking |
| Reliability | Can skip/duplicate items if data changes | More robust against data changes |
| Implementation | Simpler for basic lists | Requires stable identifiers, encoding/decoding |
| GraphQL Args | offset, limit | first, after |
When to Use Which Strategy
Cursor-based pagination is the recommended approach for most GraphQL APIs, especially those dealing with potentially large datasets or where data is frequently added or removed. It aligns with the Relay specification for connections and provides a more robust and performant solution. Offset-based pagination might be acceptable for very small, static lists where simplicity is paramount, but it's generally discouraged for production APIs.
Cursor-based pagination is the industry standard for robust and scalable GraphQL APIs, offering better performance and reliability.
GraphQL Schema Design for Pagination
A common pattern for implementing cursor-based pagination in GraphQL is the 'Connection' pattern, inspired by the Relay specification. This involves defining types for edges, nodes, and the connection itself.
The Connection pattern in GraphQL defines a structure for paginated lists. A Connection type typically includes a list of Edge types. Each Edge contains a node (the actual data item) and a cursor (an opaque identifier for that item). The Connection type also includes pageInfo which contains hasNextPage, hasPreviousPage, startCursor, and endCursor to facilitate navigation.
Text-based content
Library pages focus on text content
The primary arguments are first (to specify the number of items to return) and after (to specify the cursor of the last item from the previous page).
Cursor-based pagination is preferred because it offers better performance with large datasets and is more reliable when data is frequently added or removed, avoiding issues like skipped or duplicated items.
Learning Resources
The official specification for implementing cursor-based connections in GraphQL, crucial for understanding the Relay pattern.
A practical tutorial that explains the concepts of offset and cursor pagination and how to implement them in a GraphQL API.
This blog post provides a clear explanation of pagination strategies in GraphQL, focusing on the benefits of cursor-based methods.
Official documentation from Apollo Server on how to implement cursor-based pagination using their framework.
The official GraphQL website's section on pagination, explaining the connection pattern and its importance.
A detailed article discussing the technical advantages of cursor-based pagination over offset-based methods.
An in-depth exploration of GraphQL pagination, covering implementation details and best practices.
Prisma's guide on implementing pagination in GraphQL, offering practical advice and code examples.
A visual explanation of GraphQL pagination concepts, including the differences between offset and cursor methods.
Wikipedia's entry on Keyset Pagination (Cursor-Based Pagination), providing a general understanding of the concept.