Should I Use a Clustered Index with a GUID Primary Key?

Optimizing Table Performance with a GUID Primary Key

When dealing with large tables with primary keys based on GUIDs, performance issues can arise. GUIDs, due to their random nature, can conflict with clustered indexes, which physically order records based on the key. This can significantly slow down query performance on such tables.

Addressing Performance Issues

To resolve this issue, it is recommended to avoid using clustered indexes on GUID primary keys. Clustering works best when the data has a natural order, such as time of insertion or account numbers. For GUIDs, the ordering is random, making clustering inefficient as SQL Server constantly reorganizes records during inserts.

Best Practices for Clustering

Consider the following best practices when using clustering:

• Use clustered indexes when data has a natural order, such as date or sequence numbers.
• Avoid clustering on random or non-sequential data, like GUIDs.
• If clustering on GUIDs is unavoidable, explore alternative solutions such as replacing GUIDs with sequential or integer IDs.

By adhering to these guidelines, you can optimize the performance of tables with GUID primary keys by eliminating the performance issues associated with clustered indexes on random data.

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