Why Database Query Optimizers Underestimate Joins

In this episode of Database Tech with Fexingo, Lucas and Luna dive into a classic failure mode of query optimizers: join cardinality misestimation. Using the example of a customer analytics dashboard, they explain why optimizers often underestimate join selectivity, leading to catastrophic query plans. They explore how statistics, histograms, and correlation assumptions break down, and discuss practical fixes like extended statistics, query hints, and plan management. By the end, you'll understand why a simple-looking join can turn a sub-second query into a minutes-long disaster, and how to defend against it.

#QueryOptimization #JoinCardinality #DatabasePerformance #SQL #Statistics #Histograms #ExtendedStatistics #DatabaseTechnology #TechPodcast #FexingoBusiness #BusinessPodcast #DataEngineering #DatabaseInternals #QueryPlans #PerformanceTuning #DatabaseEngineering #LucasAndLuna #DataStorage

Keep every episode free: buymeacoffee.com/fexingo