Why is Keyset Pagination More Efficient Than OFFSET for Database Pagination?

Keyset Pagination: A Superior Alternative to OFFSET for Efficient Database Pagination

Handling large datasets often requires efficient pagination. While OFFSET is a common approach, it suffers from performance limitations. This article highlights keyset pagination as a more efficient and robust solution.

Why Keyset Pagination Trumps OFFSET

OFFSET-based pagination (rowset pagination) requires reading all rows preceding the desired page. Keyset pagination, however, uses an index to directly access the target rows, bypassing unnecessary data retrieval. This optimization significantly improves performance and eliminates the "missing row" problem inherent in OFFSET. Keyset pagination ensures data consistency by relying on unchanging keys.

Practical Implementation

Let's illustrate with a "TableName" table indexed by "Id." To fetch the initial set of records:

<code class="language-sql">SELECT TOP (@numRows) * FROM TableName ORDER BY Id DESC;</code>

Subsequent pages are retrieved using the last "Id" value from the previous query:

<code class="language-sql">SELECT TOP (@numRows) * FROM TableName WHERE Id < @lastId ORDER BY Id DESC;</code>

Notice the efficient use of the index.

Important Considerations

Effective keyset pagination demands a unique index. If your pagination relies on a non-unique column, include additional columns in both the ORDER BY and WHERE clauses to ensure uniqueness.

SQL Server's limitations necessitate a slightly more complex query:

<code class="language-sql">SELECT TOP (@numRows) *
FROM TableName
WHERE ((OtherColumn = @lastOther AND Id < @lastId) OR OtherColumn < @lastOther)
ORDER BY OtherColumn DESC, Id DESC;</code>

Handling NULL values requires careful attention and might necessitate separate queries.

In Summary

Keyset pagination offers a significant performance advantage over OFFSET. By leveraging indexes, it avoids processing unnecessary data, resulting in efficient pagination even for extremely large datasets. With proper planning and consideration for edge cases, keyset pagination provides a reliable and high-performance solution for navigating substantial data stores.

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