Cost threshold for parallelism

Question

I ran
Jonathan Kehayias's query to inspect my plan cache for costs and counts (see below for query).  Some of the costs returned were less than 5.  My server is currently configured with the default settings for MAXDOP and the cost threshold for
parallelism.  I thought the query was only reporting on queries where parallelization had occurred per the clause "WHERE  n.query('.').exist('//RelOp[@PhysicalOp="Parallelism"]') = 1".  Obviously I do not understand what
the query is doing, should I expect to see results with a StatementSubTreeCost of less than 5?
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
WITH XMLNAMESPACES
(DEFAULT 'http://schemas.microsoft.com/sqlserver/2004/07/showplan')
SELECT
query_plan AS CompleteQueryPlan,
n.value('(@StatementText)[1]', 'VARCHAR(4000)') AS StatementText,
n.value('(@StatementOptmLevel)[1]', 'VARCHAR(25)') AS StatementOptimizationLevel,
n.value('(@StatementSubTreeCost)[1]', 'VARCHAR(128)') AS StatementSubTreeCost,
n.query('.') AS ParallelSubTreeXML,
ecp.usecounts,
ecp.size_in_bytes
FROM sys.dm_exec_cached_plans AS ecp
CROSS APPLY sys.dm_exec_query_plan(plan_handle) AS eqp
CROSS APPLY query_plan.nodes('/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple') AS qn(n)
WHERE n.query('.').exist('//RelOp[@PhysicalOp="Parallelism"]') = 1

Answer 1

Looks like it returns the plans where Parallelism has been using... I suggest you reading that Jonathan's blog especially comments . As you know
SQL Server creates and runs a parallel plan for a query only when the estimated cost to run a serial plan for the same query is higher than the value set in cost
threshold for parallelism
That means if the cost of the plan is more than  5 sec  , then a parallel query will be created. So of cause you should see the costs more than 5 sec  in the output.
Best Regards,Uri Dimant SQL Server MVP,
http://sqlblog.com/blogs/uri_dimant/
MS SQL optimization: MS SQL Development and Optimization
MS SQL Consulting:
Large scale of database and data cleansing
Remote DBA Services:
Improves MS SQL Database Performance
SQL Server Integration Services:
Business Intelligence