Understanding Row Goals

Paul White has an excellent article on row goals:

In my experience, it is very common for people to miss the impact of row goals in execution plans.

No wonder, since before SQL Server 2017 CU3, there was no documented way to see information about row goals in execution plans! That update includes:

This enhancement adds the EstimateRowsWithoutRowGoal attribute to each plan operator affected by a row goal.

The new attribute is visible in all the usual places (e.g. DMVs, plan cache) but not yet in SQL Server Management Studio graphical plans (up to and including SSMS version 17.4). The SQL Server does send the new attribute, but SSMS graphical plans strip bits out that do not match its local version of the xml plan schema.

Version 17.5 of SSMS is expected to ship with an updated xml schema and UI elements, making the new attribute visible. SentryOne Plan Explorer shows the new attribute in the raw xml view already, since it doesn’t have any reason to strip the information out, but an update will be required to incorporate the new row goal information into other places (such as the Plan Diagram). I would expect it to make its way onto tooltips first.

Definitely worth a careful read.

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