Solved

SQL Query timeout on 2K8 but not 2K

Posted on 2011-09-08
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Last Modified: 2012-07-25
I wrote a SQL query a few years back against a SQL2K box that emulated a Pivot table and returned the result set in 8 secs or less.  I moved the databases to a SQL2K8 box and, with the same table structure and indexes, that same query now either times out or takes over 100 seconds to process.

What's the difference??

I've attached the query (putting literals in where variables normally go) that demonstrates the behavior.

Jeff

select 
DISTINCT 
case 
 WHEN ASSIGNMENT.COURSECODE = 'E00030' THEN ASSIGNNAME
 ELSE ASSIGNNAME + ' ('+C.COURSE+')'
 END AS ASSIGNNAME, 
assignment.assignid, 
CONVERT(VARCHAR(10),assigndate, 101) as assigndate, 
assigndate,
assignmenttype,
case substring (cast(assignscale as varchar(1)),1,1)
 WHEN 1 THEN '1-4'
 WHEN 2 THEN '1-3'
 WHEN 4 THEN '1-100'
END AS ASSIGNMENTSCALE,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol1,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol2, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol3,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol4, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol5, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol6,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol7, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol8, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol9,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol10, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol11, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol12,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol13, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol14, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol15,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol16, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol17, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol18,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol19,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol20, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol21, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol22,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol23, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol24, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol25,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol26, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol27, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol28,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol29,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol30, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol31, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '20007103') as StuCol32,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol33, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol34, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol35,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol36, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol37, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol38,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol39,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol40, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol41, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol42,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol43, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol44, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol45,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol46, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol47, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol48,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol49,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol50, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol51, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol52,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol53, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol54, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol55,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol56, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol57, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol58,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol59,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol60, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol61, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol62,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol63, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol64, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol65,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol66, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol67, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol68,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol69,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol70, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol71, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol72,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol73, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol74, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol75,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol76, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol77, 
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol78,
(select mark from assignmarks where assignid = assignment.assignid and stunum = '') as StuCol79,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC1,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC2, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC3,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC4, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC5, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC6,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC7, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC8, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC9,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC10, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC11, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC12,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC13, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC14, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC15,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC16, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC17, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC18,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC19,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC20, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC21, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC22,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC23, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC24, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC25,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC26, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC27, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC28,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC29,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC30, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC31, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '20007103') as UC32,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC33, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC34, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC35,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC36, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC37, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC38,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC39,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC40, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC41, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC42,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC43, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC44, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC45,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC46, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC47, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC48,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC49,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC50, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC51, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC52,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC53, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC54, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC55,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC56, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC57, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC58,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC59,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC60, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC61, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC62,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC63, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC64, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC65,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC66, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC67, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC68,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC69,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC70, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC71, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC72,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC73, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC74, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC75,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC76, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC77, 
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC78,
(select usecode from assignmarks where assignid = assignment.assignid and stunum = '') as UC79
from assignment
join assigncat ac on assignment.assignid = ac.assignid
join courses c on c.coursecode = assignment.coursecode
where sectcode = '106'
and assigngrade = 6
and teachcode = '120003'
and assignmenttype like 'S'
and
((ASSIGNDATE >= '08/20/2011') and (convert(varchar(12), ASSIGNDATE, 101) <= '12/31/2011'))
and
(
(ac.catcode in (select catcode from cour_cat where coursecode = 'E00030'))
and
(ac.[apply] = 1)
)
order by assignment.assigndate

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Comment
Question by:jswanberg
  • 3
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7 Comments
 
LVL 59

Expert Comment

by:Kevin Cross
ID: 36507531
jswanberg, hmm. I started to read the question and was going to say look at the "execution plan" to see what is going on. However, after reading further and seeing the query, (1) you SHOULD re-write this using PIVOT if that is what it is trying to emulate; however, (2) you seem to be grabbing the same exact value or using the same table with the same filter for a number of the columns, so a simple JOIN or CROSS APPLY to accomplish this. In a nutshell, I would recommend you rewrite this.
0
 
LVL 59

Accepted Solution

by:
Kevin Cross earned 250 total points
ID: 36507566
Couple other direct performance points to consider (execution plan review should provide factual support):
- (convert(varchar(12), ASSIGNDATE, 101) <= '12/31/2011') is better written as ASSIGNDATE < '01/01/2012' -- i.e., ASSIGNDATE < DATEADD(dd, 1, '12/31/2011') -- otherwise, your index on ASSIGNDATE is potentially not going to be used.
- (ac.catcode in (select catcode from cour_cat where coursecode = 'E00030')), this may be hurting you -- you can try (exists(select 1 from cour_cat cc where cc.catcode = ac.catcode and coursecode = 'E00030')) or simply add an inner join based on your data.
- Expanding on the "based on your data" above, I would look at the relationships as I see you are using DISTINCT. If you can return your query in a unique manner in the first place, you can eliminate that potential overhead.
- assignmenttype like 'S' should just be assignmenttype = 'S' -- not really a performance thing, juts more correct since you are not doing any patterns there.
- check for unnecessary implicit conversions. You know your data, but for example something like this looks interesting:

case substring (cast(assignscale as varchar(1)),1,1)
 WHEN 1 THEN '1-4'
 WHEN 2 THEN '1-3'
 WHEN 4 THEN '1-100'
END AS ASSIGNMENTSCALE

You are converting a variable to a VARCHAR(1) then substring() it from the 1st character for 1 character, then compare the result to integers in CASE/WHEN.

Hope that helps you get going. Post back once you have tried something and we can help you through the process.
0
 

Author Comment

by:jswanberg
ID: 36507672
Yeah I knew that it needed rewriting especially since PIVOT didn't exist in 2K but does in 2K8.  I was more interested in the meantime in why the exact same query responded in 2K one way and so much more of a drag in 2K8.

Is it something in the structure that I can change to make it perform like 2K while I'm simultaneously rewriting the query??

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LVL 59

Expert Comment

by:Kevin Cross
ID: 36507767
Run the explain plan and we can see exactly what is going on. There is so many things there, it could be indexing or something like that. It may have worked in 2k, but with change in database engine and query optimizer since then the query is being treated in some different way ... could be something silly, so looking at the execution plan will help narrow it down.
0
 

Assisted Solution

by:jswanberg
jswanberg earned 0 total points
ID: 36507794
There is no individual execution cost; the issue is the 160 separate nested queries now make up 97% cost to the overall but each one is only showing a 1% hit.  There are no hits against suggested indexes.

Looks like I'm stuck until I can rewrite the query to use the PIVOT command.
0
 
LVL 3

Expert Comment

by:hspoulsen
ID: 36509301
Is this a new SQL Server 2008?

If so, did you update the stats?
or
Rebuild indexes, then update stats?

If you are not the only user on the database, were you blocked by others?
(use Sp_whoisactive shows this)

Best regards,
Henrik Staun Poulsen, Stovi Software
0
 

Author Closing Comment

by:jswanberg
ID: 38222036
Gave insight on other items in the query that could be affecting performance without having to rewrite as a PIVOT query
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