SQL Server Execution Plans - Red Gate Software

Chapter 3: Text and XML Execution Plans for Basic Queries
|--Index Seek
(OBJECT:([AdventureWorks2008R2].[HumanResources].
[Employee].[AK_Employee_LoginID] AS [e]),
SEEK:([e].[LoginID]=CONVERT_IMPLICIT(nvarchar(4000),[@1],0)) ORDERED FORWARD)
Listing 3.3
The DefinedValues column for a given PLAN_ROW contains a comma-delimited list of the
values that the operator introduces to the data flow between operators. These values may
be present in the current query (in the SELECT or WHERE clauses), as is the case for our
Index Seek operator, where this column contains:
[e].[BusinessEntityID], [e].[LoginID]
Listing 3.4
Alternatively, they could be internal (intermediate) values that the query processor needs
in order to process the query. Think of DefineValues as a temporary holding place for
values used by the query optimizer as the operators execute.
Finally, note from the EstimateRows column that the Index Seek operation produces an
estimated one row.
Next, Line 4 (NodeID 5), a Clustered Index Seek against HumanResources.Employee.
This immediately illustrates what I would regard as a weakness with text plan format. It is
not immediately obvious, as it was with the graphical plan, that this operation is, in fact,
a Key Lookup operation. We need to scan through the whole contents of the StmtText
column to find this out (Listing 3.5).
|--Clustered Index Seek
(OBJECT:([AdventureWorks2008R2].[HumanResources].
[Employee].[PK_Employee_BusinessEntityID] AS [e]),
SEEK:([e].[BusinessEntityID]=[AdventureWorks2008R2].[HumanResources].
[Employee].[BusinessEntityID] as [e].[BusinessEntityID])
LOOKUP ORDERED FORWARD)
Listing 3.5
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