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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(137.6, 40%, 23%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ES%3C/text%3E%3C/svg%3E)
why is that.? my cost of parallelism is default 5
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(35.2, 30%, 13%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ETH%3C/text%3E%3C/svg%3E)
The cut-off value is for the whole query, not an individual operator. Also, it is for the serial plan. I.e. force a serial plan and look at the estimated subtree cost for the whole query. This is what the sp_configure value is compared to.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(185.6, 95%, 27%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EAB%3C/text%3E%3C/svg%3E)
Hi,
During compilation, the optimizer will consider a serial plan. If the cost of the serial plan exceeds your threshold of 5, the optimizer will then consider a parallel plan. If the parallel plan is less costly than the serial plan, SQL will use that. So, I'd guess that the serial plan cost was > 5, though the parallel plan is not. You could try forcing a serial plan with a query hint to see what the cost is.
Thanks
Andrew
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(73.60000000000001, 21%, 17%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EDB%3C/text%3E%3C/svg%3E)
The parallel plan is often more costly than the serial plan, but uses more resources to get done more quickly.
the cost of this plan shown in the screen is the total subtree cost.
You are showing us one operator in the plan, with its subtree cost of 2.426. What is relevant is the subtree cost for the whole plan! The subtree cost you see for the outermost Select operator.
no . that's point to the "select" operator already