Question

SQL Queries run at different performance

Asked by: Corey_819

Hello and sorry to bother everyone with probably an easy question, but I am stuck. What I have is an Select statement I run in one SQL database and it runs very quick less than a second. However, if I go to the same database schema just more data in the tables and run the exact same query I am running at 9 - to 10 seconds. I have ran the SHOW Plan XML and the one database takes the query down one plan/path and the other one take it down another plan/path. Any thoughts based on what you may see in the plan that I am not.

1st plan takes 9 - to 10 seconds
2nd plan take which is different and the one thing I am not sure why takes less than a second. 

select distinct dbo . CV3BasicObservation . ItemName , dbo . CV3BasicObservation . ArrivalDtm , dbo . CV3BasicObservation . Value from dbo . CV3BasicObservation inner join dbo . CV3ResultCatalogItem on dbo . CV3BasicObservation . ResultItemGUID = dbo . CV3
   |--Stream Aggregate(GROUP BY:([UH1].[dbo].[CV3BasicObservation].[ArrivalDtm], [UH1].[dbo].[CV3BasicObservation].[ItemName], [UH1].[dbo].[CV3BasicObservation].[Value]))                                                                                       
        |--Parallelism(Gather Streams, ORDER BY:([UH1].[dbo].[CV3BasicObservation].[ArrivalDtm] ASC, [UH1].[dbo].[CV3BasicObservation].[ItemName] ASC, [UH1].[dbo].[CV3BasicObservation].[Value] ASC))                                                           
             |--Nested Loops(Inner Join, OUTER REFERENCES:([UH1].[dbo].[CV3CatalogClassTypeValue].[CatalogMasterGUID], [Expr1018]) WITH ORDERED PREFETCH)                                                                                                        
                  |--Sort(ORDER BY:([UH1].[dbo].[CV3BasicObservation].[ArrivalDtm] ASC, [UH1].[dbo].[CV3BasicObservation].[ItemName] ASC, [UH1].[dbo].[CV3BasicObservation].[Value] ASC))                                                                        
                  |    |--Hash Match(Inner Join, HASH:([UH1].[dbo].[CV3ResultCatalogItem].[OrderMasterItemGUID])=([UH1].[dbo].[CV3CatalogClassTypeValue].[CatalogMasterGUID]), RESIDUAL:([UH1].[dbo].[CV3ResultCatalogItem].[OrderMasterItemGUID]=[UH1].[dbo].[CV
                  |         |--Parallelism(Distribute Streams, Broadcast Partitioning)                                                                                                                                                                           
                  |         |    |--Merge Join(Inner Join, MERGE:([UH1].[dbo].[CV3ResultCatalogItem].[GUID])=([UH1].[dbo].[CV3BasicObservation].[ResultItemGUID]), RESIDUAL:([UH1].[dbo].[CV3BasicObservation].[ResultItemGUID]=[UH1].[dbo].[CV3ResultCatalogItem
                  |         |         |--Index Scan(OBJECT:([UH1].[dbo].[CV3ResultCatalogItem].[CV3ResultCatalogItemPK]), ORDERED FORWARD)                                                                                                                       
                  |         |         |--Sort(ORDER BY:([UH1].[dbo].[CV3BasicObservation].[ResultItemGUID] ASC))                                                                                                                                                 
                  |         |              |--Nested Loops(Inner Join)                                                                                                                                                                                           
                  |         |                   |--Index Seek(OBJECT:([UH1].[dbo].[CV3ClientVisit].[CV3ClientVisitPK]), SEEK:([UH1].[dbo].[CV3ClientVisit].[GUID]=[@0]) ORDERED FORWARD)                                                                         
                  |         |                   |--Parallelism(Gather Streams)                                                                                                                                                                                   
                  |         |                        |--Clustered Index Scan(OBJECT:([UH1].[dbo].[CV3BasicObservation].[BasicObservationClustIdx]), WHERE:([UH1].[dbo].[CV3BasicObservation].[ClientVisitGUID]=[@0] AND [UH1].[dbo].[CV3BasicObservation].[Arriva
                  |         |--Index Scan(OBJECT:([UH1].[dbo].[CV3CatalogClassTypeValue].[CV3CatalogClassTypeValuePK]))                                                                                                                                          
                  |--Clustered Index Seek(OBJECT:([UH1].[dbo].[CV3OrderCatalogMasterItem].[CV3OrderCatalogMasterItemPK] AS [CV3OrderCatalogMasterItem]), SEEK:([CV3OrderCatalogMasterItem].[GUID]=[UH1].[dbo].[CV3CatalogClassTypeValue].[CatalogMasterGUID]) ORD
 
 
 
 
select distinct dbo . CV3BasicObservation . ItemName , dbo . CV3BasicObservation . ArrivalDtm , dbo . CV3BasicObservation . Value from dbo . CV3BasicObservation inner join dbo . CV3ResultCatalogItem on dbo . CV3BasicObservation . ResultItemGUID = dbo . CV3
  |--Stream Aggregate(GROUP BY:([Replica_UH1].[dbo].[CV3BasicObservation].[ArrivalDtm], [Replica_UH1].[dbo].[CV3BasicObservation].[ItemName], [Replica_UH1].[dbo].[CV3BasicObservation].[Value]))                                                               
       |--Nested Loops(Inner Join)                                                                                                                                                                                                                              
            |--Index Seek(OBJECT:([Replica_UH1].[dbo].[CV3ClientVisit].[CV3ClientVisitPK]), SEEK:([Replica_UH1].[dbo].[CV3ClientVisit].[GUID]=[@0]) ORDERED FORWARD)                                                                                            
            |--Parallelism(Gather Streams, ORDER BY:([Replica_UH1].[dbo].[CV3BasicObservation].[ArrivalDtm] ASC, [Replica_UH1].[dbo].[CV3BasicObservation].[ItemName] ASC, [Replica_UH1].[dbo].[CV3BasicObservation].[Value] ASC))                              
                 |--Nested Loops(Inner Join, OUTER REFERENCES:([CV3OrderCatalogMasterItem].[GUID]))                                                                                                                                                             
                      |--Sort(ORDER BY:([Replica_UH1].[dbo].[CV3BasicObservation].[ArrivalDtm] ASC, [Replica_UH1].[dbo].[CV3BasicObservation].[ItemName] ASC, [Replica_UH1].[dbo].[CV3BasicObservation].[Value] ASC))                                           
                      |    |--Nested Loops(Inner Join, OUTER REFERENCES:([Replica_UH1].[dbo].[CV3ResultCatalogItem].[OrderMasterItemGUID]))                                                                                                                     
                      |         |--Nested Loops(Inner Join, OUTER REFERENCES:([Replica_UH1].[dbo].[CV3BasicObservation].[ResultItemGUID]))                                                                                                                      
                      |         |    |--Clustered Index Scan(OBJECT:([Replica_UH1].[dbo].[CV3BasicObservation].[BasicObservationClustIdx]), WHERE:([Replica_UH1].[dbo].[CV3BasicObservation].[ClientVisitGUID]=[@0] AND [Replica_UH1].[dbo].[CV3BasicObservation
                      |         |    |--Index Seek(OBJECT:([Replica_UH1].[dbo].[CV3ResultCatalogItem].[CV3ResultCatalogItemPK]), SEEK:([Replica_UH1].[dbo].[CV3ResultCatalogItem].[GUID]=[Replica_UH1].[dbo].[CV3BasicObservation].[ResultItemGUID]) ORDERED FOR
                      |         |--Clustered Index Seek(OBJECT:([Replica_UH1].[dbo].[CV3OrderCatalogMasterItem].[CV3OrderCatalogMasterItemPK] AS [CV3OrderCatalogMasterItem]), SEEK:([CV3OrderCatalogMasterItem].[GUID]=[Replica_UH1].[dbo].[CV3ResultCatalogIte
                      |--Clustered Index Seek(OBJECT:([Replica_UH1].[dbo].[CV3CatalogClassTypeValue].[MasterAndClassTypeClustIdx]), SEEK:([Replica_UH1].[dbo].[CV3CatalogClassTypeValue].[CatalogMasterGUID]=[Replica_UH1].[dbo].[CV3OrderCatalogMasterItem].[GU

                                  
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Asked On
2009-10-26 at 16:18:26ID24845623
Topics

SQL Server 2005

,

SQL Query Syntax

Participating Experts
1
Points
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Comments
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Answers

 

by: DanielWilsonPosted on 2009-10-26 at 16:32:20ID: 25668070

It may be valid to use a different execution plan based on different amounts of data.  However, if the indexes and/or statistics are out of date, the server will not make an informed decision.

Try rebuilding the indexes & statistics & see if that solves the problem.

 

by: Corey_819Posted on 2009-10-26 at 16:36:52ID: 25668093

Thanks DanielWilson that is a good idea. Quick question I noticed and sorry for not posting that I had  over logical reads 2151348 in a table this constantly being updated. Would this cause my MERGE and RESIDUAL Hash to have to work in this plan vs. the other database that is not being updated as much in the table I am querying and joining? Just a thought.

 

by: DanielWilsonPosted on 2009-10-26 at 17:09:38ID: 25668254

I don't know.

But a table that is being constantly updated has potential for getting the indexes / statistics out of date rather quickly.

If this solves your problem, you'll want to schedule rebuilds ... often I do it weekly, but you may want to do it nightly if you're really getting a lot of updates.

 

by: Corey_819Posted on 2009-10-27 at 10:52:46ID: 31646208

Thanks Daniel you have been awesome help.

20120131-EE-VQP-002

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