SQL Server 2008 :: Execution Plan Ignoring Index Insisting On Key Lookup
Sep 15, 2015
I have query with an expensive Key Lookup on a joined table. The predicate is the column that I'm joining on, and the output list contains two columns from the joined table.
I've created a basic non-clustered index covering the predicate column and include-ing the two output columns. However, the execution plan ignores this, and insists on using the primary key of the joined table to do the expensive key lookup. I've tried adding the included columns to the index directly and there's no change. I've also tried running dbcc freeproccache and no change.
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Jun 17, 2015
I run a query
select col1, col2, col3, col4
from Table
where col2=5
order by col1
I have a primary key on the column.The execution plan showing the clustered index scan cost 30% & sort cost 70%..When I run the query I got missing index hint on col2 with 95% impact.So I created the non clustered index on col2.The total executed time decreased by around 80ms but I didn't see any Index name that is using in the execution plan.After creating the index also I am seeing same execution plan
The execution plan showing the clustered index scan cost 30% & sort cost 70% but I can see the total time is reducing & Logical reads on that table is reducing.I am sure that index is useful but why there is no change in the execution plan?
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Dec 10, 2006
If you display the execution plan and run the following:SET STATISTICS IO ONgoSELECT ProductID, SupplierIDFROM ProductsWHERE SupplierID = 1I don't understand how come there is noBookmark Lookup operation happening to get theProductID?I only see an Index Seek happening on SupplierID.There is no composite index SupplierID + ProductIDso what am I not understanding here?Thank you
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Jun 17, 2015
Is it possible to check query execution plan of a store procedure from create script (before creating it)?
Basically the developers want to know how a newly developed procedure will perform in production environment. Now, I don't want to create it in production for just checking the execution plan. However they've provided SQL script for the procedure. Now wondering is there any way to look at the execution plan for this procedure from the script provided?
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Jun 4, 2015
how to eliminate a key lookup from the execution plan
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
SET NOCOUNT ON
SELECT COUNT(ph.lid) AS Total
FROM PLB ph
WHERE ph.lPhysician = @Physician
AND ph.BSF = CAST(0 AS bit)
[code]....
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Jun 25, 2015
Is there a way to leave the graphical 'Include Execution Plan' on by default in SSMS? I don't know how many times I run a long-running query, say to myself, "wow, that took a while; I wonder what the execution plan looks like?" only to realize that I left it turned off. Now I have to turn it on, and wait for the query to run again. I'm guessing there's a setting in the options somewhere to always leave it on, but I'm not sure where
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Oct 30, 2014
I'm in the process of trying to optimize a stored procedure with many queries. The execution plan provides a missing non-clustered index on nearly every query, and they're all fairly similar. The only real difference between them are what's in the INCLUDE statement. The two key columns are listed in every missing index. Let's say each query is approximately 5% of the total batch and 90% of the queries all fall into the category I listed above. How should I go about creating the missing indexes? Create all of the missing indexes or create one generic one that has all the INCLUDE columns? Create a minimal index with just a few of the common INCLUDE columns?
Here's an example of what I'm talking about with the missing indexes:
/*
USE [DB]
GO
CREATE NONCLUSTERED INDEX [<Name of Missing Index, sysname,>]
ON [dbo].[TABLE_1] ([COLUMN_A],[COLUMN_B])
INCLUDE ([C4ABCD],[C4ARTX],[C4ASTX],[C4ADNB],[C4AFNB],[C4BKVA])
GO
*/
/*
The Query Processor estimates that implementing the following index could improve the query cost by 99.9044%.
*/
/*
USE [DB]
GO
CREATE NONCLUSTERED INDEX [<Name of Missing Index, sysname,>]
ON [dbo].[TABLE_1] ([COLUMN_A],[COLUMN_B])
INCLUDE ([C4ARTX],[C4ASTX],[C4ADNB],[C4CZST])
GO
*/
/*
The Query Processor estimates that implementing the following index could improve the query cost by 99.5418%.
*/
/*
USE [DB]
GO
CREATE NONCLUSTERED INDEX [<Name of Missing Index, sysname,>]
ON [dbo].[TABLE_1] ([COLUMN_A],[COLUMN_B])
INCLUDE ([C4ABCD],[C4ARTX],[C4ASTX],[C4ADNB],[C4AFNB],[C4BKVA])
GO
*/
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Mar 14, 2015
Is only one plan is kept for one query in plan cache?
i heard generally hash is created for a query and plan is search with this hash.
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Jun 28, 2006
Hi,
Can you please tell me the way to configure the LOOK UP transformation so that it will ignore all the null values ? I want to configure a Look up component for the column "Col1" as follows
All the NULL values of Col1 should not be considered for look-up process. They should be passed to the downstream component as valid rows.
All NOT NULL values of Col1 should be processed by the Look up component.
If there is no matching value present for any NOT NULL value of Col1 then it should be directed to error output.
Regards,
Gopi
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Jul 7, 2006
The benefit of the actual execution plan is that you can see the actual number of rows passing through each step - compared to the estimated number of rows.But what about the "cost percentages" ?I believe I've read somewhere that these percentages is still just an estimate and is not based on the real execution.Does anyone know this and preferable have a link to something that documents it?Thanks
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Oct 20, 2006
please explain the differences btween this logical & phisicall operations that we can see therir graphical icons in execution plan tab in Management Studio
thank you in advance
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Feb 22, 2008
Can anyone explain me simple language and easy to understand query execution plan. I am a fresher assigned to read and evaluate execution plan. i do not understand where is the problem. what percentage is considered as good sql and what percentage is considered as bad sql.
how do i understand whether there is a problem in sql or joins or index or anything else. Please explain me step by step what should be considered and what recomenendation should i give for each problem.
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May 29, 2004
As a developer, we always say "using a stored procedure, instead of a cliet side SQL statement, provides performance benefits". However, it seems it has not been true anymore since SQL Server 7.0.
See SQL online "Execution Plan Caching and Reuse" at http://msdn.microsoft.com/library/default.asp?url=/nhp/default.asp?contentid=28000409
I am quite confused with the following questions:
1. it seems since SQL 7.0, a SQL statement in client side uses the existing execution plan as a stored procedure does. That means SP doesn't has much advantage over SQL statement in terms of performance.
2. It seems, a stored procedure is not always compled ONLY once. If a stored procedure is not used for a long time, it could be kicked out from procedure cashe.
3. In order to use an existing execution plan, it seems that we have to use the fully qualified identifier, such as
SELECT * FROM Northwind.dbo.Employees
instead of
SELECT * FROM Employees
However, I rarely see anyone uses these kind of fully qualified references for objects both in SQL statements and SP. For example, in the sample database pubs and NorthWind, they don't use the fully qualified expression. I only see the use of it in master database.
I guess I might miss something in the issues above. I would like to get any explanation from SQL guru or anybody. Thanks a lot.
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Nov 27, 2014
I have 2 tables,
1. Need
2. NeedCategory
Need table has clusted index on needid column and NeedCategory have composite clustered index on needid and categoryid.
Now take a look on following query and execution plan for the query.
SELECT N.NeedId,N.NeedName,N.ProviderName
FROM dbo.Need N
JOIN dbo.NeedCategory NC
ON nc.NeedId = n.NeedId
WHERE IsActive=1
AND CategoryId= 2
ORDER BY NeedName
* Clustered index scan on need table is happens for Isactive= 1.
* Clustered index scan on needcategory table is happens for CategoryId=2
My question is,
1. Why scan happens before the join occurs? if it happens after join then the filter would be lighter. Even if optimizer chooses the scan to execute first.
2. Is there any chance to rearrange the execution plan manually?
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Jan 15, 2007
Hi
I am having a query
SELECT Dur1.rootId
FROM DurableEventTab Dur1
WHERE (Dur1.dev_ReferenceClusterRoot = 'iyrwd.52' )
AND Dur1.dev_Action = 'Order:Ordered')
AND (Dur1.dev_Active = 1) AND (Dur1.dev_PurgeState = 0)
AND (Dur1.dev_PartitionNumber = 0)
This table has a primary key : aribapk11
and the indexes on the dev_ReferenceClusterRoot,
dev_Action,dev_purgestate .
Now when I fire this query
the query execution plan is actaull doing a Clustered Index scan on the PK :aribaPK11 . What I was expecting was an index seek on the key defined on dev_referenceClusterRoot. Please not the index seek is the behaviour in sql server 2000.
Any idea what is going wrong ?
Clustered Index Scan(OBJECT:([typhoon1902].[dbo].[DurableEventTab].[AribaPK7] AS [Dur1]), WHERE:([typhoon1902].[dbo].[DurableEventTab].[dev_Active] as [Dur1].[dev_Active]=(1.) AND [typhoon1902].[dbo].[DurableEventTab].[dev_PurgeState] as [Dur1].[dev_PurgeState]=(0) AND [typhoon1902].[dbo].[DurableEventTab].[dev_PartitionNumber] as [Dur1].[dev_PartitionNumber]=(0) AND [typhoon1902].[dbo].[DurableEventTab].[dev_ReferenceClusterRoot] as [Dur1].[dev_ReferenceClusterRoot]='iyrwd.52' AND [typhoon1902].[dbo].[DurableEventTab].[dev_Action] as [Dur1].[dev_Action]=N'Order:Ordered')) 0 0 Clustered Index Scan Clustered Index Scan OBJECT:([typhoon1902].[dbo].[DurableEventTab].[AribaPK7] AS [Dur1]), WHERE:([typhoon1902].[dbo].[DurableEventTab].[dev_Active] as [Dur1].[dev_Active]=(1.) AND [typhoon1902].[dbo].[DurableEventTab].[dev_PurgeState] as [Dur1].[dev_PurgeState]=(0) AND [typhoon1902].[dbo].[DurableEventTab].[dev_PartitionNumber] as [Dur1].[dev_PartitionNumber]=(0) AND [typhoon1902].[dbo].[DurableEventTab].[dev_ReferenceClusterRoot] as [Dur1].[dev_ReferenceClusterRoot]='iyrwd.52' AND [typhoon1902].[dbo].[DurableEventTab].[dev_Action] as [Dur1].[dev_Action]=N'Order:Ordered') [Dur1].[rootId] 1 0.00386574 0.0002263 71 0.00409204 [Dur1].[rootId] PLAN_ROW 0 1
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Nov 11, 2014
I'm new to using SQL Server. I've been asked to optimize a series of scripts that queries over 4 millions records. I've managed to add indexes and remove a cursor, which increased performance. Now when I run the execution plan, the only query that cost is a DELETE statement from the main table. It shows a SORT which cost 71%. The table has 2 columns and a unique index. Here is the current index:
ALTER TABLE [dbo].[Qry] ADD CONSTRAINT [Qry_PK] PRIMARY KEY NONCLUSTERED
(
[QryNum] ASC,
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = ON, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
Question: Will the SORT affect the overall performance? If so, is there anything I should change within the index that would speed up my query?
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Apr 30, 2008
I have a person table with 1 billion rows on it, partitioned equally at 10 million rows per partition. The primary key constraint is a composite of an identity column and ssn( char(11) ) with the partitioning column built on the SSN.
This is built on my home grown workstation:
Microsoft 2008 Server 64 bit, Microsoft SQL server 2008 64 bit, Intel 2.66 quad core, 8 gb ram, Os/ raid 1, data on 6 drives hardware/software raid 50, transaction logs on 4 drive raid 10, all drives sata II/ 3gb burst.
I have updated statistics on the table and I have 2 queries that give clustered index seek , one never comes back before I get impatient, the other comes back instantly, and the showplan looks the same for both queries.
SELECT *
FROM Person
WHERE PersonKey > -1 and SSN = '219-09-3987'
AND
SELECT TOP 100 PERCENT *
FROM Person
WHERE PersonKey > -1 and SSN = '219-09-3987'
Incidentally the query with the top 100 percent is the one that returns instantly.
I am puzzled
1) Why the estimated plan looks the same
2) Why a top 100 Percent query is faster than one without it
Timothy A. Vanover
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May 1, 2015
In sp_create_plan_guide documentation, it's written:
When SQL Server matches the value of statement_text to batch_text and @parameter_name data_type [,...n ], or if @type = 'OBJECT', to the text of the corresponding query inside object_name, the following string elements are not considered:
White space characters (tabs, spaces, carriage returns, or line feeds) inside the string.
Comments (-- or /* */).
Trailing semicolons
On SQL Server 2008 SP3, I created a plan guide for a query. Now, if I execute the query exactly how it was defined in the plan guide, SQL Server match it and use the plan guide to optimize the query.
However, if I add just a space between a column name and an operator in the WHERE clause, the plan guide is ignored. How come it doesn't ignore the extra space, like mentioned in the documentation?
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May 6, 2015
Looking at an execution plan today I noticed something I've not seen before. The plan includes a non clustered index seek, followed by a RID lookup on the heap. The output list for the index seek contains the expected "Bmk" column (in this case "Bmk1473"), but also includes "IsBaseRow1475". This isn't a column from the table.
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Mar 8, 2015
We have a view with many left joins. The original creators of this view might have been lazy or sloppy, I don't know. I have rewritten the query to proper inner joins where required and also nested left joins.
So rather then the following exemplary fragment
select <many items>
from A
left join B on B.id_A = A.id
left join C on C.id_B = B.idthis now looks like
select <many items>
from A
left join (B
join C on C.id_B = B.id
) on B.id_A = A.id
Compilation time of the original view was 18s, of the new rewritten view 4s. The performance of execution is also better (not counting the compile of course). The results of the query are identical. There are about 30 left joins in the original view.
I can imagine that the optimizer has difficulty with all these left joins. But 14s is quite a big difference. I haven't looked into detail in the execution plans yet. I noticed that in both cases the Reason for Early Termination of Statement Optimization was Time Out.
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Mar 6, 2015
One of my programmers changed their database from full to Simple recovery. Saw that my job that backs up the Full Recovery mode databases failed, so I moved that database to my Simple database backup job plan and removed it from the Full Recovery job. I am unable to remove the db from the Transaction Log task on the Full Plan because when I try to edit that job "Databases with Simple Recovery will be excluded"
My transaction log backups are still failing with the following error: "The statement BACKUP LOG is not allowed while the recovery model is SIMPLE. Use BACKUP DATABASE or change the recovery model using ALTER DATABASE. BACKUP LOG is terminating abnormally.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly.Just want to remove that database so my Full Recovery backup job does not try to back it up.
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Apr 29, 2015
I have inherited a server on which is a maintenance plan with two subplans on different schedules. In each subplan there are Execute T-SQL tasks with scripts for index rebuilds. Each task is set up with a Completion arrow to the next task and a Failure arrow to a Notify Operator Task. I was asked to add a task for index rebuilds to a specific subplan for a specific database, which is what the other tasks also do. I discovered that my task was failing but the others were fine. No notification was sent about my task failing even though the job is marked in MSDB as a failed job. I have sent a test email using the "Send Test Email..." option when right clicking Database Mail in SSMSand I receive an email so I know Database Mail works.
I set up a test job to model the index job that I can't get notifications from. I have two T-SQL tasks that just select the top row from a small table. The first task has a syntax error that I did so it would fail. I have a failure arrow to a Notify Operator Task and a Completion arrow to another T-SQL task with no syntax error which has a Success arrow to a Notify Operator task. As expected, when I execute this job I receive one failure email and one success email.
The only other troubleshooting step I know to try is to add a Notify Operator task before my failing task. That Notify Operator task will hopefully fire to tell me that the previous step was successful. I am not having problems with the other steps so I was just thinking I would try to get the subplan to send me a success email about one of the steps that has been working fine.
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Aug 21, 2001
I'm new to SQL server but familiar enough with databases to know this doesn't seem right.
Here's the situation:
I have a table with real estate property information. There are about 650,000 rows in it. I have a nonclustered non-unique index on the city where the property is located. There are about 40 unique values in this index.
I do a simple query like:
SELECT city,address from propinfo where city= 'CARLSBAD'. The query will return about 4,000 rows. The problem is that the execution plan that it chooses is to do a full table scan. I.E. Even though there is an index on City, it chooses to look through 650,000 rows rather than do an index seek. Something sounds inefficient here. BTW, this happens in both SQL 7 and SQL 2000. Can anyone explain why this happens? I've got to think that SQL Server is more efficient here.
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Feb 2, 2006
Hello, I have been looking at the execution plan for a procedure call and the select, compute scalar, stream aggregates, constant scan, nested loops, asserts are all at 0% cost, the PK costs are 2% apart from a rogue 7% and a few 20%, tables scans are all at 23%. The query cost realtive to the batch is 100%. What does this all mean?
I have put non-clustered indexes on all the table attributes that are involved in the select statements but this has made no difference, i am guessing this is because my tables are not heavily populated and i may have seen a difference if i had thousands of entries in the tables the select statements acted on, is this assumption correct?
Does anyone else bother using the execution plan to tweak there DB or is it a negligible tool?
Jill
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Aug 29, 2007
In sql server 2005 management studio where do I find the option to run the sql query in the query analyser and also show the execution plan?
At present I see the option under Query menu which is "Display estimated Execution plan" which only shows the plan but does not execute the query.
Thanks
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Feb 29, 2008
Does anyone know of a good way to copy the execution plan when using "Include Actual Execution Plan"?
I often need to copy this and mail it.
I know I can use PrintScreen button, but I need a more efficient way to do this.
If I just could rightclick the execution plan and select "Copy" and get complete plan it would be great.
Mladen?
E 12°55'05.25"
N 56°04'39.16"
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Jul 20, 2005
Which of the following does NOT cause the execution plan of a query to berecompiled ?- new column is added to a table accessed by a query OR- index used by a query has been dropped from the database OR- query perfoms a join to return data from multiple tables OR- significant amount of data in a table has been mofified
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Jul 20, 2005
Hi,I have a table-valued user defined function (UDF) my_fnc.The execution of statement "select * from my_fnc" takes much longertime than runnig the code inside my_fnc (with necessary changes).What can be the reason?How can I see an execution plan used for UDF?Thanks a lotMartin
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Jul 29, 2015
I am replicating a stored procedure execution, which builds and executes the following dynamic SQL command:
IF EXISTS (select * from MyDB..sysfiles sf (nolock) where name = 'MyDB_201201')
ALTER DATABASE [MyDB] REMOVE FILE [MyDB_201201]
IF EXISTS (select * from MyDB..sysfilegroups sfg (nolock)
where groupname = 'MyDB_201201' and sfg.groupname not in(
SELECT distinct fg.name file_group_name
[Code] ....
I can run this SP with no errors on both the publisher and the subscriber. However, when I try to replicate the execution of this SP, I get an error in replication monitor:
ALTER DATABASE statement not allowed within multi-statement transaction. (Source: MSSQLServer, Error number: 226)
How can I change my code to workaround this? Perhaps some explicit transactions?
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Sep 8, 2015
I have an issue with DBCC Check DB maintenance plan . I run it in my production last nite.
After running for 1 hour , the package failed ( the step failed )
As below :
Executed as user: ETSPDCSQL1-VWSYSTEM. ....0.5500.0 for 64-bit Copyright (C) Microsoft Corp 1984-2005. All rights reserved. Started: 22:06:13 Progress: 2015-09-08 22:06:14.11 Source: {F0BABEC1-ECBF-4B7D-86BE-7C2C99A08ED8} Executing query "DECLARE @Guid UNIQUEIDENTIFIER EXECUTE msdb..sp...".: 100% complete End Progress
[Code] .....
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Sep 9, 2015
I would like to view the previous executed query error message in SSMS. Is there any way to view the query execution error messages history in SSMS?
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Jul 9, 2007
Hi,I want to access the real execution plan via my webapplication after I have executed an SQL statement. I know how to get the estimated execution plan:1 cmd.CommandText = "SET SHOWPLAN_XML ON";2 cmd.ExecuteNonQuery();3 4 cmd.CommandText = myStatement;5 SqlDataReader dataReader = cmd.ExecuteReader();6 7 String plan = String.Empty;8 9 while (dataReader.Read()) {10 plan += dataReader.GetSqlString(0).ToString();11 }12 13 cmd.CommandText = "SET SHOWPLAN_XML OFF";14 cmd.ExecuteNonQuery();I want do compare the estimated costs with the real costs of the same statement. If I change code line 1 an 13 to "SET STATISTICS XML [ON|OFF]" the string "plan" will contain the result of the submitted SELECT statement, but I just need to get the plan and not the result itself. Thanks in Advance,Dominik
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Jul 28, 1999
What does 'tablename. index... cost: 100%' mean when I use display estimated execution plan?
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