DB Engine :: Cost Vs Time When Including Actual Query Plan In SSMS

Nov 11, 2015

I have two queries yielding the same result that I wanted to compare for performance. I did enter both queries in one Mangement Studio query window and execute them as one batch with the actual query plan included.Query 1 took 8.2 seconds to complete and the query plan said that the cost was 21% of the batchQuery 2 took 2.3 seconds to complete and the query plan said that the cost was 79% of the batch.The queries were run on my local development machine. I was the only user. No other programs were running at the time of this test. The results are repeatable.I understand that the query with the lowest cost is not necessarily the fastest query. On the other hand, the difference is quite big. The query that has approx. 80% of the cost takes 20% of the time and the other way around. I have two questions:

Is such a discrepancy normal?Can conclusions be drawn from the cost distribution? For instance, does the query that takes 8.2 seconds but only costs 21% scale better?

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Jul 25, 2006

I have a view in SQLServer 2005. It took 30 sec. to finish. Then I deleted 4500 records from one table that is used in view. It took 90 sec. to finish now. I did a comparison on Actual Execution Plan between before I deleted data and after I deleted data, they are almost same, only different is Actual Number Rows become less after deleted data. So, I wonder why data become less but time become more. When I look closely on the Actual Execution Plan, the ridiculous thing is, there are only Estimated Operation Cost on each step, no Actual Operation Cost. I guess there are something wrong with optimizer because reuse same Execution Plan, but how can I tell which step wrong without Actual Operation Cost.

Thanks!

Henry

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I know that the subtree cost is a way to gauge the performance of a query against other queries, but I have typically seen the cost go in the same direction as the execution time (they both go up or the both go down).

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I would appreciate any help on this matter.

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Code:
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select col1 from table1 (nolock) where col1 like '%ABC%'

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Query 1: Query cost (relative to the batch): 0%
select col1 from table1 (nolock) where col1 like '#,%ABC%' or col1 like 'BC,%ABC%'
----------------------------------------------------------------------------------------------------------------------------
SELECT Index Seek
Cost:0% <------- [DB1].[dbo].[table1].[Idx..]

Cost: 100%


Query 2: Query cost (relative to the batch): 100%
select col1 from table1 (nolock) where col1 like '%ABC%'
----------------------------------------------------------------------------------------------------------------------------
SELECT Index Scan
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Cost: 100%

------------------------------------------------STAT TIME-----------------------------------------------------------
SQL Server parse and compile time:
CPU time = 0 ms, elapsed time = 1 ms.

SQL Server Execution Times:
CPU time = 0 ms, elapsed time = 1 ms.
SQL Server parse and compile time:
CPU time = 0 ms, elapsed time = 7 ms.

(3 row(s) affected)
Table 'table1'. Scan count 2, logical reads 2932, physical reads 0, read-ahead reads 18, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(1 row(s) affected)

SQL Server Execution Times:
CPU time = 938 ms, elapsed time = 943 ms.

(3 row(s) affected)
Table 'table1'. Scan count 1, logical reads 2927, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(1 row(s) affected)

SQL Server Execution Times:
CPU time = 515 ms, elapsed time = 505 ms.
SQL Server parse and compile time:
CPU time = 0 ms, elapsed time = 1 ms.

SQL Server Execution Times:
CPU time = 0 ms, elapsed time = 1 ms.

------------------------------------------------STAT TIME-----------------------------------------------------------

As expected, SARGable Query 1 did a nonclustered index seek and nonSARGable Query 2 did an index scan instead. According to the query plan, Query 1 consumed 0% relative to the batch whereas Query 2 is 100%. When I checked the CPU time, I was a bit confused because Query 1 showed CPU time of 938ms whereas Query 2 showed 515ms. I triple checked and every time I got similar results. I am sure I'm missing something, could someone please tell me what I'm missing? Thanks a bunch!

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Hello everyone!

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[code]....

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1server:
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2server:
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Hi,



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I also would like to know how do mining models store the data.

Do they store the data in the same table/view format
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I have 2 different queries which produce same result. I want to know which querry is better and why?
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Queries are the following

Query A



Code Snippet

SELECT EmployeeDetails.FirstName+' '+EmployeeDetails.LastName AS EmpName,
COUNT(LUP_EmpProject.Empid) AS Number_Of_Projects
FROM LUP_EmpProject
INNER JOIN EmployeeDetails
ON LUP_EmpProject.Empid=EmployeeDetails.Empid
GROUP BY EmployeeDetails.FirstName+' '+EmployeeDetails.LastName,
LUP_EmpProject.Empid
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AND COUNT(LUP_EmpProject.Empid)=(SELECT
MAX(Number_Of_Projects)
FROM (SELECT COUNT(LUP_EmpProject.Empid) Number_Of_Projects
FROM LUP_EmpProject
GROUP BY LUP_EmpProject.Empid)AS sub)


Query B



Code Snippet

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EmployeeDetails.FirstName + ' ' + EmployeeDetails.LastName AS EmpName,
COUNT(*) AS NumberOfProjects
FROM LUP_EmpProject
INNER JOIN EmployeeDetails
ON LUP_EmpProject.EmpID = EmployeeDetails.EmpID
GROUP BY LUP_EmpProject.EmpID,
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HAVING COUNT(*)=(SELECT
MAX(Number_Of_Projects)
FROM (SELECT COUNT(LUP_EmpProject.Empid) Number_Of_Projects
FROM LUP_EmpProject
GROUP BY LUP_EmpProject.Empid)AS sub



Please Help!!!!!!!!!!!!!!!!1

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SELECT 
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I’ve been looking at Paul White’s article: [URL] ....
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[code]....

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