Is Keyset Pagination a Better Alternative to SQL Server's OFFSET for Efficient Data Pagination?

Beyond SQL Server OFFSET paging: the efficiency advantage of Keyset paging

Paging technology is crucial when dealing with large data sets, as it allows us to obtain specific parts of the data efficiently. Although SQL Server provides the OFFSET clause for paging, it has a performance bottleneck. This article will explore an alternative that performs better than OFFSET: Keyset paging.

Keyset paging: a better paging mechanism

Keyset paging adopts a more efficient mechanism than the row number-based Rowset paging used by OFFSET. Instead of reading all previous rows, it allows the server to directly access the correct location in the index, minimizing redundant reads.

To successfully implement Keyset paging, a unique index needs to be established on the primary key (and any other relevant columns). This enables the paging mechanism to navigate data based on primary keys rather than row numbers.

Advantages of Keyset paging

In addition to significant performance improvements, Keyset paging has other advantages:

• Avoid losing rows: Unlike OFFSET, it eliminates the risk of losing rows due to deletion as the primary key remains unchanged.
• Direct primary key access: It allows direct access to a specific primary key without the need for page estimation.

Keyset paging example

Suppose there is a table called 'TableName' with an index on the 'Id' column. The starting query for paging is as follows:

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

Subsequent requests can retrieve the next page:

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

Notes on Keyset paging

• The selected primary key must be unique, or combined with other columns to ensure uniqueness.
• If the pagination primary key is not unique, additional columns should be included in the index and considered in the query.
• SQL Server does not support tuple comparators and requires specific comparisons when using non-unique primary keys.

Conclusion

For paging of large data sets, Keyset paging proves to be a superior alternative to SQL Server OFFSET. Its efficiency, direct primary key access, and ability to avoid missing rows make it ideal as the best data retrieval option in paging scenarios.

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