Execution Plans - SQLCE 3
Jun 21, 2006Does SQLCE 3 cache execution plans? Or even make use of them?
Thanks
Tryst
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Execution Plans &<&> Proportionate Execution Times
Dec 7, 2005Hi I am slowly getting to grips with SQL Server. As a part of this, I have been attempting to work on producing more efficient queries. This post is regarding what appears to be a discrepancy between the SQL Server execution plan and the actual time taken by a query to run. My brief is to produce an attendance system for an education establishment (I presume you know I'm not an A-Level student completing a project :p ). Circa 1.5m rows per annum, testing with ~3m rows currently. College_Year could strictly be inferred from the AttDateTime however it is included as a field because it a part of just about every PK this table is ever likely to be linked to. Indexes are not fully optimised yet. Table:CREATE TABLE [dbo].[AttendanceDets] ([College_Year] [smallint] NOT NULL ,[Group_Code] [char] (12) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,[Student_ID] [char] (8) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,[Session_Date] [datetime] NOT NULL ,[Start_Time] [datetime] NOT NULL ,[Att_Code] [char] (1) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ) ON [PRIMARY]GO CREATE CLUSTERED INDEX [IX_AltPK_Clust_AttendanceDets] ON [dbo].[AttendanceDets]([College_Year], [Group_Code], [Student_ID], [Session_Date], [Att_Code]) ON [PRIMARY]GO CREATE INDEX [All] ON [dbo].[AttendanceDets]([College_Year], [Group_Code], [Student_ID], [Session_Date], [Start_Time], [Att_Code]) ON [PRIMARY]GO CREATE INDEX [IX_AttendanceDets] ON [dbo].[AttendanceDets]([Att_Code]) ON [PRIMARY]GOALL inserts are via an overnight sproc - data comes from a third party system. Group_Code is 12 chars (no more no less), student_ID 8 chars (no more no less). I have created a simple sproc. I am using this as a benchmark against which I am testing my options. I appreciate that this sproc is an inefficient jack of all trades - it has been designed as such so I can compare its performance to more specific sprocs and possibly some dynamic SQL. Sproc:CREATE PROCEDURE [dbo].[CAMsp_Att] @College_Year AS SmallInt,@Student_ID AS VarChar(8) = '________', @Group_Code AS VarChar(12) = '____________', @Start_Date AS DateTime = '1950/01/01', @End_Date as DateTime = '2020/01/01', @Att_Code AS VarChar(1) = '_' AS IF @Start_Date = '1950/01/01'SET @Start_Date = CAST(CAST(@College_Year AS Char(4)) + '/08/31' AS DateTime) IF @End_Date = '2020/01/01'SET @End_Date = CAST(CAST(@College_Year +1 AS Char(4)) + '/07/31' AS DateTime) SELECT College_Year, Group_Code, Student_ID, Session_Date, Start_Time, Att_Code FROM dbo.AttendanceDets WHERE College_Year = @College_YearAND Group_Code LIKE @Group_CodeAND Student_ID LIKE @Student_IDAND Session_Date <= @End_DateAND Session_Date >=@Start_DateAND Att_Code LIKE @Att_CodeGOMy confusion lies with running the below script with Show Execution Plan:--SET SHOWPLAN_TEXT ON--Go DECLARE @Time as DateTime Set @Time = GetDate() select College_Year, group_code, Student_ID, Session_Date, Start_Time, Att_Code from attendanceDetswhere College_Year = 2005 AND group_code LIKE '____________' AND Student_ID LIKE '________'AND Session_Date <= '2005-11-16' AND Session_Date >= '2005-11-16' AND Att_Code LIKE '_' Print 'First query took: ' + CAST(DATEDIFF(ms, @Time, GETDATE()) AS VarCHar(5)) + ' milli-Seconds' Set @Time = GetDate() EXEC CAMsp_Att @College_Year = 2005, @Start_Date = '2005-11-16', @End_Date = '2005-11-16' Print 'Second query took: ' + CAST(DATEDIFF(ms, @Time, GETDATE()) AS VarCHar(5)) + ' milli-Seconds'GO --SET SHOWPLAN_TEXT OFF--GOThe execution plan for the first query appears miles more costly than the sproc yet it is effectively the same query with no parameters. However, my understanding is the cached plan substitutes literals for parameters anyway. In any case - the first query cost is listed as 99.52% of the batch, the sproc 0.48% (comparing the IO, cpu costs etc support this). BUT the text output is:(10639 row(s) affected) First query took: 596 milli-Seconds (10639 row(s) affected) Second query took: 2856 milli-SecondsI appreciate that logical and physical performance are not one and the same but can why is there such a huge discrepancy between the two? They are tested on a dedicated test server, and repeated running and switching the order of the queries elicits the same results. Sample data can be provided if requested but I assumed it would not shed much light. BTW - I know that additional indexes can bring the plans and execution time closer together - my question is more about the concept. If you've made it this far - many thanks.If you can enlighten me - infinite thanks.
View 10 Replies View RelatedExecution Plans
Nov 16, 2001I have two schematically identical databases on the same MS SQL 2000 server. The differences in the data are very slight. Here is my problem: the identical query has totally different execution plans on the different databases. One is (in my opinion) correct, the other causes the query to take 60 times as long. This is not an exaggeration, on the quick DB the query takes 3 seconds, on the other DB it takes 3 minutes. I have tried the following to help the optimizer pick a better execution plan on the slow db:
rebuild the indexes
dbcc indexdefrag
update statistics
I CAN put in a hint to cause the query to execute faster, but my employer now knows about the problem and he (and I) want to know WHY this is happening.
Any ideas would be greatly appreciated.
Thanks.
-Scott
Execution Plans
Jul 23, 2005HiCan you give me sone pointers to where I can get more information aboutthe various operations like index seeks,Bookmark Lookups,ClusteredIndex Scan in an execution plan.ThanksRagu
View 2 Replies View RelatedPermissions To See Execution Plans
Apr 15, 2008Hi Gurus,
What permissio0ns one should have to view execution plans on SQL SERVER 2005.
Thanks,
ServerTeam
SQL Server Execution Plans
Jul 23, 2005I'm looking for assistance on a problem with SQL Server. We have adatabase where a particular query returns about 3000 rows. This querytakes about 2 minutes on most machines, which is fine in thissituation. But on another machine (just one machine), it can run forover 30 minutes and not return. I ran it in Query Analyzer and it wasreturning about 70 rows every 45-90 seconds, which is completelyunacceptable.(I'm a developer, not a DBA, so bear with me here.)I ran an estimated execution plan for this database on each machine,and the "good" one contains lots of parallelism stuff, in particularthe third box in from the left. The "bad" one contains a "Nested Loop"at that position, and NO parallelism.We don't know exactly when this started happening, but we DO know thatsome security updates have been installed on this machine (it's at theclient location), and also SP1 for Office 2003.So it looks like parallelism has been turned off by one of these fixes.Where do we look for how to turn it back on? This is on SQL Server2000 SP3.Thanks for any help you might have for me!Christine Wolak -- SPL WorldGroup --Join Bytes!
View 6 Replies View RelatedSame Query - Different Execution Plans??
Jul 16, 2007Hi,We are trying to solve a real puzzle. We have a stored procedure thatexhibits *drastically* different execution times depending on how itsexecuted.When run from QA, it can take as little as 3 seconds. When it iscalled from an Excel vba application, it can take up to 180 seconds.Although, at other times, it can take as little as 20 seconds fromExcel.Here's a little background. The 180 second response time *usually*occurs after a data load into a table that is referenced by the storedprocedure.A check of DBCC show_statistics shows that the statistics DO getupdated after a large amount of data is loaded into the table.*** So, my first question is, does the updated statistics force arecompile of the stored procedure?Next, we checked syscacheobjects to see what was going on with theexecution plan for this stored procedure. What I expected to see wasONE execution plan for the stored procedure.This is not the case at all. What is happening is that TWO separateCOMPILED PLANs are being created, depending on whether the sp is runfrom QA or from Excel.In addition, there are several EXECUTABLE PLANs that correspond to thetwo COMPILED PLANs. Depending on *where* the sp is run, the usecountincreases for the various EXECUTABLE PLANS.To me, this does not make any sense! Why are there *multiple* compileand executable plans for the SAME sp?One theory we have is, that we need to call the sp with the dboqualifier, ie) EXEC dbo.spHas anyone seen this? I just want to get to the bottom of this andfind out why sometimes the query takes 180 seconds and other timesonly takes 3 seconds!!Please help.Thanks much
View 5 Replies View RelatedParameter && Execution Plans.
May 8, 2007Hi all,
I have a table TableA with few million rows. When I query TableA , the execution plans changes based on the input parameter as shown below . Why this happens ? How to resolve this ? Any inputs would be appreciated.
SELECT * FROM TableA WHERE Column1 = 1 => SELECT -> Clustered Index Scan (100%)
SELECT * FROM TableA WHERE Column1 = 2 => SELECT -> Clustered Index Scan (100%)
SELECT * FROM TableA WHERE Column1 = 3 => SELECT -> Parallelism (3%) -> Clustered Index Scan (97%)
SELECT * FROM TableA WHERE Column1 = 4 => SELECT -> Nested Loops -> Index Seek (50%) -> Clustered Index Seek (50%)
(takes a very long time to retrieve the records)
Thanks in advance,
DBLearner.
How To Interprete Execution Plans For Queries
Dec 16, 2004Pls tell me where i will be able to find a good material on interpreting the Execution plans................how do i compare 2 diff plans for Quries written in 2 diff ways...giving same output
View 2 Replies View RelatedSQL Server: Execution Plans + Statistics
Jan 13, 2004In using ADO to connect to SQL Server, I'm trying to retrieve multiple datasets AND statistics that are usually returned via the OnInfoMessage event. For those that are familiar with SQL Server, I need the results returned by the SET STATISTICS IO ON and SET STATISTICS PROFILE ON options. Anyone had any luck doing this before?
Thanks in advance.
Execution Plans Inconsistent With Performance
May 16, 2008I've been working with SQL Server 2005 for a while now and I've noticed some odd behavior that I want to bounce of other members of the community. I should preface that I've been a forum viewer (and occasional contributer) here at SQL Team for a while and I've naturally developed a keen sense for optimizations.
Fundamentally, longer stored procedures with perfectly fine/optimized execution plans are inconsistent with real world performance. In some of these cases, a low subtree cost on a 4 core machine with 16gb of ram and 2 15 drive SAS arrays with little load takes excessively long to run or in some cases doesn't complete.
This isn't due to blocking or resource bottlenecks as I'm quite familiar with built in tools to troubleshoot and resolve those issues. In all cases, I am able to rearchitect the stored procedure into a higher subtree cost variant and get reasonable performance, but it's frustrating to have to redo work and there seems to be no common theme other than longer multi-statement procedures.
I've used SQL Server 2000 extensively and did not notice this level of inconsistency in performance with that product version. Just wondering if others in the community have experiences similar or if I'm just crazy.
Thanks for reading my rant.
- Shane
Different Execution Plans - Same Data, Same Server
Jul 23, 2005Hi there - hoping someone can help me here!I have a database that has been underperforming on a number of queriesrecently - in a test environment they take only a few seconds, but onthe live data they take up to a minute or so to run. This is using thesame data.Every evening a copy of the live data is copied to a backup 'snapshot'database on the same server and also, on this copy the queries onlytake a second or so to run. (This is testing through the QueryAnalyser)I've studied the execution plans for the same query on the snapshot dband the live db and they seem to be significantly different - why isthis? it's looking at the same data and exactly the same code!!Anybody got any ideas???
View 3 Replies View RelatedPossible To Have Multiple Query Execution Plans For A Stored Procedure?
Feb 21, 2013I think not. Microsoft says it is possible: one for parallel and one for serial execution. Don't believe that's possible for a stored procedure to change execution plans on the fly. Have an on-going problem with timeout occurring with an application and narrowed the culprit to a stored procedure. I couldn't find any obvious issues database wise, no locks, etc. so I recompiled (altered) the sproc without making any changes and the issue cleared for a couple days.
It happened again to day, and so I recompiled (altered) the sproc and it went away again. No code changes to both application (so they say) and stored procedure. I ran the below code snippet to check for sprocs with multiple cached plans and the offending one came up on a short list. So, my question is, Is it one sproc per query plan or can there be more than one. I understand the connection issues.
Code:
SELECT db_name(st.dbid) DBName,
object_schema_name(st.objectid, dbid) SchemaName,
object_name(st.objectid, dbid) StoredProcedure,
MAX(cp.usecounts) Execution_count,
st.text [Plan_Text]
INTO #TMP
[Code] .....
Left Join Vs Left Outer Join Syntax Generates Different Execution Plans
Apr 16, 2008
Anyone know why using
SELECT *
FROM a LEFT OUTER JOIN b
ON a.id = b.id
instead of
SELECT *
FROM a LEFT JOIN b
ON a.id = b.id
generates a different execution plan?
My query is more complex, but when I change "LEFT OUTER JOIN" to "LEFT JOIN" I get a different execution plan, which is absolutely baffling me! Especially considering everything I know and was able to research essentially said the "OUTER" is implied in "LEFT JOIN".
Any enlightenment is very appreciated.
Thanks
Sqlce 3.0 Vs Sqlce 2.0 Memory Issue
Feb 6, 2006I am currently upgrading our ppc app (written in .net 2003) to .net 2005 and from sqlce 2.0 to 3.0. The new application runs out memory(storage) when handling lots of data transactions (both in case of using sqlcedatareader, and dataset ). There is no memory leak issue here, sqlce 3.0 simply uses a lot more (3 times more) memory than sqlce 2.0.
Our applicaton runs fine using sqlce 2.0 and .net 2003, but fail due to memory shortage
with the upgrades(which has the same code). Anyone can shed some lights on this issue?
How Do You Use The Upgrade.exe For Sqlce 2.0 To Sqlce 3.0?
Jun 9, 2006Does anyone have any instructions on how to go about uprading a .sdf file
from sqlce 2.0 to sqlce 3.0?
I found this on an msdn website
(link: http://www.microsoft.com/sql/editions/sqlmobile/upgrading.mspx) but
as you can see its very lacking on detail. (I included the link and content
referring to upgrading the database files so you won't have to go to the link
to see the part referring to upgrading the database.) I tried to run the upgrade.exe on my device but it doesn't explain how you're supposed to point it to the .sdf that you are trying to update. Here is the content on the above web page.
Upgrading Database Files
You can upgrade a database created with an earlier version of SQL Server CE
2.0 to a database created with SQL Server Mobile by using the SQL Server
Mobile Database Upgrade tool (upgrade.exe). The Database Upgrade tool runs on
a smart device.
When you run the SQL Server Mobile Database Upgrade tool, the new SQL Server
Mobile database is created on the smart device. The new database, with the
file name extension .sdf, contains all the data that was in the source
database. You need to reinitialize the upgraded database to continue using it
for replication.
Note: If you are using replication or remote data access (RDA) as a
connectivity solution before upgrading to SQL Server Mobile, you must
synchronize the source SQL Server CE database (subscription database) with
the SQL Server database (Publisher). The reason for synchronizing before
upgrading to SQL Server Mobile is to ensure that any changes that exist in
the tables on the SQL Server CE database are updated on the SQL Server
database, because after the upgrade you must resubscribe or repull using the
new database.
SQLCE 2.0 And SQLCE 3.0, Both On Same Server
Oct 11, 2006I presently run on my server SQL SERVER CE 2.0 and want to install, in addition on SQL Server 2.0, SQL Server Mobile 2005.
Is there a procedure to have both installed and running on a computer?
Thanks!
Marco
Static Variables In A SQLCLR Stored Proc Seem To Get Reused From Execution To Execution Of The Sp
Aug 23, 2007after moving off VS debugger and into management studio to exercise our SQLCLR sp, we notice that the 2nd execution gets an error suggesting that our static SqlCommand object is getting reused from the 1st execution (of the sp under mgt studio). If this is expected behavior, we have no problem limiting our statics to only completely reusable objects but would first like to know if this is expected? Is the fact that debugger doesnt show this behavior also expected?
View 4 Replies View RelatedExecution Procedure Stored During Execution Of The Report .
Aug 3, 2007
Hello :
How to execute a procedure stored during execution of the report, that is before the poster the data.
Thnak you.
Execution In Scheduled Job Vs Direct Execution
Nov 29, 2004Here's my case, I have written a stored procedure which will perform the following:
1. Grab data from a table using cursor,
2. Process data,
3. Write the result into another table
If I execute the stored procedure directly (thru VS.NET, or Query Analyser), it will run, but when I tried to execute it via a scheduled job, it fails.
I used the same record, same parameters, and the same statements to call the stored procedure.
Any idea?
SqlCE To SQL 2k5
May 16, 2007It is possible to upgrade existing SqlCE to Sql 2k5 database? Or just import CE database to import data model structure and data?
View 1 Replies View RelatedSqlce 3.5 Won't Run On Asp.net
Dec 12, 2007My app is working on my local system with the vs2008 development server. It's an asp.net app and I added the line:
AppDomain.CurrentDomain.SetData("SQLServerCompactEditionUnderWebHosting", true);
So it works fine on my system. But I can't get it to work on shared hosting. I have uploaded all the sqlce 3.5 dlls to the bin directory. I am stuck at the error:
Access to the database file is not allowed. [ File name = ]
There actually is a file name in the connection string, and I set the permissions wide open on App_Data to test this.
What are the .net framework requirements for sqlce 3.5? I can't find this info anywhere.
I know sqlce 3.5 is not recommended for asp.net, but it is not the main site database but is used for a setup database utility to be installed for a windows app.
SQLCE 3.5 For X86 CE 4.2 Redistributable
Jan 31, 2008Hi,
We have over 1000 terminals running CE 4.2 on an x86 cpu currently using SQLCE 3.1.
We have just upgraded to VS 2008 and found the projects have been upgraded to reference SQL CE 3.5 - this is great, as we wish to use things like TOP etc.
However, all the distributable packages only include CAB files for CE 4.2 for the ARM Processor, or CE 5.0 for the x86. Is there a CAB package available for CE 4.2 for the x86 CPU? (please...)
Even just the relevant .DLL files would be fine as we repackage them ourselves anyway.
Thanks.
Oracle To SQLCe
Mar 21, 2007Hi,
Could some one in copying data from Oracle to MS SQLCe, I have the entire table structure on SQLCe.
I want to do it progamatically, if there is tool which will do this activity I am also fine with that.
Which SqlCe Cab File I Can Use
Apr 2, 2007Hi i developed Wm5 PPC application with sqlce database. i Create Cab file when i install in my HP WM5 PPC that will showe the Message sqlcewm.dll missed. Please tell me 1)sqlce30.ppc.wce5.armv4i 2)sqlce30.wce5.armv4i 3)sqlce20.ppc.wce5.armv4i..Please Help me
View 1 Replies View RelatedNativeException In SQLCE?
Oct 23, 2007
In my homegrown data layer, I added the ability to do Order By Clauses.
I do one query with an Order By clause (all 6 records in the table retrieved).
Then I do a 2nd query without an Order By (36 of around 200 records in the table retrieved)
And I'm getting Native Exceptions.
ExceptionCode: 0xc00000000c (Null Pointer I believe)
ExceptionAddresss: 0x00c3703c (looks to be in sqlcese30.dll)
Reading: 0x00000005
I ran thru with the debugger, and am finding the error happening inside of a SQLDataReader.Read() call. It's trying to read the 14th of the 36 records that the query has found.
I am all but positive I'm not closing this database connection. The problem is happening while I'm looping off the reader data I just retrieved and in this query there was no ORDER BY clause.
I'm at a loss as to what to do about this. I'm not explicitly closing any database connections, and I'm getting the data right after performing the query.
Is It Just Me Or Are There BIG Problems With SQLCE 3.0?
Oct 4, 2007Greetings,
I wrote a very simple C# console application which was designed to give us a rough idea on the performance and reliability of SQLCE (the source code without metrics has been posted to this group recently). What I've found is that there are major performance and reliability issues with SQLCE 3.0 as opposed to SQLCE 2.0. Whereas SQLCE 2.0 seems to be fairly consistent in terms of it's memory usage and the amount of time taken to insert rows into the table regardless of the size of the table (to a limit, after about 300,000 records it too has major performance issues), SQLCE 3.0 seems to slow down noticably and continually use more memory even after a few thousand records are inserted and actually crashes (consistently) after 25592 records are inserted!
What gives? Based on this it would seem that SQLCE 2.0 is far preferable for an unattended device that needs an uptime of over 30 days whilst constantly (several times per minute) inserting into the database.
Thanks for your thoughts on this...
SQLCE 3.5 Sync BUG
Mar 3, 2008I'm using SQL'05, VS'08 SQLCE 3.5 building VB.NET applications.
I'm using LocalDataCache to sync SQLCE and SQL'05
When I write a new record to SQLCE the corresoponding record in SQL'05 shows both LastEditDate and CreationDate values.
When I update the recored in SQLCE the LastEditDate gets updated, but CreationDate gets set to NULL.
Ideas?
David L.
SQL 2005 To SQLCe
Mar 20, 2007Hi,
Could some one guide me hot copy tables/Data from SQL 2005 to Sql 2005 Compact Edition?
Thanks
SQLCE And WPF Examples?
Jan 3, 2007Hello all,
I want to use SQLCE and WPF.
Can anyone direct me to some example code.
two way binding with a sqlceResultSet would be a great start.
(last inquiry was in Aug of 06)
Thanks
Mike (still trying to get the latest tech to work together) Greenway
Upgrading SqlCE 3.1 To 3.5
Apr 13, 2007Hi,
Does anybody know how to upgrade a SqlCE db(.sdf) file from Version 3.1 to 3.5?
And a URL where can I get related Info.
Sqlce Utility Need Help
Nov 8, 2007Last month , I have made a utility named sqlce viewer to help me manage sqlce 3.5 beta version databases .
The location is https://sourceforge.net/projects/sqlceviewer/
And now , I encounter a strange problem , need some help .
After user install this utility or run it standalone execute file .There has a error message poped before see the login in form . Even user has installed .net framework version 3.5 .
And if user has installed visual studio 2008 beta2 ,this problem will not existed .
This utility depend on these components :
1)WPF
2).net framework 3.5 beta
I don't know what's the reason clearly .
Anyone could give some advice are warm welcome.
SSMSE With SQLCE
May 31, 2007can anyone tell me how to open/create a SQL Server 2005 Compact Edition database using SQL Server Management Studio Express?
cheers