Understanding Probe Residuals

Daniel Janik explains what a probe residual is in an execution plan:

A probe residual is important because they can indicate key performance problems that might not otherwise be brought to your attention.

What is a probe residual?

Simply put, a probe residual is an extra operation that must be performed to compete the matching process. Extra being left over things to do.

Click through for an example brought about by implicit conversion.

Related Posts

Table Variables And Parallelism

Erik Darling shows your brain on table variables: Inserts and other modifications to table variables can’t be parallelized. This is a product limitation, and the XML warns us about it. The select could go parallel if the cardinality estimate were more accurate. This could potentially be addressed with a recompile hint, or with Trace Flag […]

Read More

Non-Blocking Aggregations

Daniel Hutmacher tilts at windmills: It’s not entirely uncommon to want to group by a computed expression in an aggregation query. The trouble is, whenever you group by a computed expression, SQL Server considers the ordering of the data to be lost, and this will turn your buttery-smooth Stream Aggregate operation into a Hash Match […]

Read More

Categories

April 2017
MTWTFSS
« Mar May »
 12
3456789
10111213141516
17181920212223
24252627282930