SSMS : Execution plan sometimes exceeds 100% - by AaronBertrand

Status : 

  By Design<br /><br />
		The product team believes this item works according to its intended design.<br /><br />
		A more detailed explanation for the resolution of this particular item may have been provided in the comments section.


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ID 267530 Comments
Status Closed Workarounds
Type Bug Repros 4
Opened 4/3/2007 2:13:12 PM
Access Restriction Public

Description

Several elements in the execution plan are labeled as 100%, in this case the total is > 570%.  I have seen this periodically with complex queries against indexed views, but I am not positive indexed views have anything to do with it.
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Posted by GaneshC on 3/4/2015 at 2:11 AM
Hi,

I am using SQL Server 2008 and I am also getting the same thing i.e. query cost - Clustered Index Scan, XML Reader with XPath filter is taking more than 100 % and in some cases it;s showing 5/6 digit %.
Posted by Matija Lah on 9/19/2008 at 1:34 AM
Please, document this behavior/anomaly in Books Online. The explanation makes sense, but it's far from what anyone would expect, so it needs explicit clarification.
Posted by Microsoft on 5/28/2008 at 11:58 AM
Thanks again for bringing this to our attention. This anomaly arise in the presence of "row goals" and the concatenation operator. Row goals is the term for when a subtree (perhaps the entire query) is not required to return all possible rows. This most commonly happens when the query has a "top" clause although there are other causes. The anomaly arises because we do not expect to execute the second child of the Concatenation (because we expect the first child to provide all the required rows). Those additional children are costed to assume they return a single row. The only alternative would be to give them 0 cost which would fix the anomaly but probably create other confusions and would lead the optimizer to not care about the plans - we don't want to do that just in case they are executed.

Campbell Fraser, SQL Development.
Posted by Microsoft on 4/10/2007 at 8:40 AM
Hi Aaron,
    Thank you for submitting your feedback regrading Showplan showing strange percentages. I've forwarded this on to the showplan team to figure out what is going on.
Thank you,
Bill Ramos