Estimated I/O cost, a sign of an expected spill
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Some execution plan properties get a lot of attention. Others tend to be mostly overlooked. But even those properties can, sometimes, relay interesting information. Estimated Operator Cost The Estimated Operator Cost property is one of those that does get a lot of attention. Perhaps even too much. When you look at an execution plan in SQL Server Management Studio, or in Azure Data Studio., it conveniently marks each operator with a line such as “Cost: 34%”. And some third party tools, such as SentryOne’s Plan Explorer, even go a step further and color code this cost in red, yellow, or…
