My New developerWorks Article: Why Low-Cardinality Indexes Negatively Impact Performance

My second developerWorks article has been published! This is a bit of a technical deep dive into a question that was running around my head earlier in the year. Give it a read and let me know what you think!

Low cardinality indexes can be bad for performance. But, why? There are many best practices like this that DBAs hear and follow but don’t always understand the reason behind. This article empowers DBAs to understand the logic behind why low cardinality indexes can be bad for performance or cause erratic performance. The topics this article covers include B-tree indexes, understanding index cardinality, hypothetical examples of the effects of low cardinality indexes, a real-world example of the effects of a low cardinality index, and tips on how to identify low cardinality indexes and reduce their impact on performance.

Figure 4 appears to be missing for some reason. I have notified developerWorks and they are fixing it. In different colors, it looks something like this:

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