Parallelism in SQL Server Execution Plan

Question

I was trying to optimize my query and I've come across a Parallelism show plan operator, which I have not yet encountered before.

Was wondering, what is this for, and what does it indicate if it is included in an execution plan?

Thanks!

Solution

A Parallelism operator in a SQL Server execution plan shows that multiple threads will perform the work. For example, if the optimiser calculates that an operation would benefit from and can be split into multiple streams, it distributes into multiple streams of execution, performs the task in separate streams and then gathers the multiple streams back into a result set.

The Parallelism operator performs the distribute streams, gather streams, and repartition streams logical operations.

If you haven't seen it already: Execution Plan Basics

Distribute streams execution plan icon

Gather streams execution plan icon

Repartition streams execution plan icon