Prevent Stored Procedure Timeout
Write efficient Stored Procedures
Prevent More Disk Reads
Prevent Dead Locks
System.Data.SqlClient.SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
The following are the collection of my learning as a SQL developer.
Because of large data on the tables, the join operations and other operations will take up lot of time hence causing the application to time out, also reducing the performance.
Parameter SniffingIn short, parameter sniffing is one exec plan for all parameter combinations.
- This option causes the compilation process to ignore the value for the specified variable and use the specified value instead.
- Unlike the other workaround (Option(Recompile)), this option avoid the overhead of recompiling the query every time.
This is the most common problem, The workaround is to declare the input params again with different variable name and use the
new variable through out the SP.
In the Example @local_SetupId
CREATE PROCEDURE [dbo].[pr_get_user_ids]
(
@in_SetupId int
)
As
begin
Declare@local_SetupIdint=@in_SetupId
Select UserIdfrom UserDetailwhere SetupId=@local_SetupId
end
Use Local Temp Tables
Store the data from large tables such as Product / Orders/ Hierarchyinto Local temp Tables and Use them when joining – This is will Prevent the joining of heavy tables.
This is Subject to temp Db Size. Consider the temp Db size.
Select only the needed columns for your Transaction operation and put it into a local temp table. Hence on performing joins the tables will be lighter and preventing the use of excess Resource.
In the Example We have filtered out few columns from productHierarchytable using setupid in Where clause and used it to join with Product table.
SELECT * into #TempProductHierarchyFROM
(SELECT ProductHierarchy,ProductHierarchyId,ProductIdfromProductHierarchyDetails where SetupId=@local_SetupId)ASTPH
SELECT ProductCodeInterfacefrommasters.ProductP
inner join #tempProductHierarchyonP.ProductId=#TempProductHierarchy.ProductId
Instead of
SELECT ProductCodeInterface frommasters.Product P
inner join masters.ProductHierarchyDetail PHD onP.ProductId=PHD.ProductId
where P.SetupId=@local_SetupId
Use NON Clustered Index
Use Non Clustered Index on temp tables for quicker Execution
Once you have created a temp table, set index on the primary key of the table – on which you will be performing the join operation.
In the example we have read the Product Hierarchy table into a temp table and we have created a non-clustered index onto the primary key i.e ProductId
SELECT*into#TempProductHierarchyFROM
(SELECT ProductHierarchy,ProductHierarchyId,ProductIdfromProductHierarchyDetails
where SetupId=@local_SetupId)ASTPH
Create NonClusteredIndexIDX_TP4 On#TempProductHierarchy(ProductId)
Use With(NOLOCK)
NOLOCK typically (depending on your DB engine) means give me your data, and I don't care what state it is in, and don't bother holding it still while you read from it. It is all at once faster, less resource-intensive
Use NOLOCK on master tables and not everywhere.
Using NoLockmay become dangerous sometimes, so check the query exec plan when in doubt.
Select * from ProductHierarchy WITH(NOLOCK)
Join On the InputParameter
This will reduce the operation size and the disk read
Join on input parameter instead of filtering in where condition.
As you can see here we have joined on setupid i.e the input parameter instead of joining on the setupid of the other table and then filtering in where condition.
SELECT * from trans.PromotionP
inner join masters.ProductPP with(NOLOCK) on PP.SetupId=@local_SetupId
inner join masters.CustomerCC with(NOLOCK)onCC.SetupId=@local_SetupId
Instead Of
SELECT * from trans.PromotionP
inner join masters.ProductPP with(NOLOCK) on PP.SetupId=P.SetupId
inner join masters.CustomerCC with(NOLOCK)onCC.SetupId=P.SetupId
Where PP.SetupId=@local_SetupId
Prevent the use of “Select *”
Causes Indexing issues and Binding issues
Dont use "SELECT *" ina SQLquery
Insead use Select ProductId, ProductName from Products
Use EXISTS
To check if any data exists in a particular table, use EXISTS instead of relying on Count its more effective.
SELECT OrderId,AmendVersionFROMtrans.OrdersWHEREEXISTS(SELECTtop 1 OrderId FROMtrans.OrderExtract WHERESetupId=1099)
Use Local Temp Tables (#TempTableName)
Prevent using Global hash tables (##)
SELECT * into #TempProductFROM(SELECTProductId,LevelId,ProductCodeInterface,NamefromProduct whereSetupId=@local_SetupIdandIsActive=1)ASTP
Use Local Variables to Store the FunctionCall return
Prevent calling the string functions or date functions Over and over again, instead store ‘em in local variables if you are going to reuse the value.
Declare@sampleStringvarchar(max)='nevermind the promotions'
Declare @sizeOfStringint
set @sizeOfString=len(@sampleString)
SELECT @sizeOfString
Use Try - Catch
BEGIN TRY
-- Logic / Query here
END TRY
BEGIN CATCH
-----------------------------------------------------------------------
DECLARE
@ErrMsg VARCHAR(255)-- Error Message
,@ErrNo INT -- Error Number
,@ErrSeverityINT -- Error Severity
,@ErrProc VARCHAR(255)-- Error Procedure
,@ErrLine INT -- Error Line
SELECT
@ErrMsg = ERROR_MESSAGE()
,@ErrNo = ERROR_NUMBER()
,@ErrSeverity=17
,@ErrProc = ERROR_PROCEDURE()
,@ErrLine = ERROR_LINE()
RAISERROR (
@ErrMsg
,@ErrSeverity
,1
,@ErrNo
,@ErrLine
,@ErrProc
)
-----------------------------------------------------------------------
END CATCH
END
Use SET NOCOUNT ON
Whenever we write any procedure and execute it a message appears in message window that shows number of rows affected with the statement written in the procedure.
When SET NOCOUNT is ON, the count is not returned.
SETNOCOUNTON
Select PromotionId from Promotion
Prevent Usage of DDL Statements
Do not try to use DDL statements inside a stored procedure that will reduces the chance to reuse the execution plan.
DDL statements like CREATE,ALTER,DROP,TRUNCATE etc.
DDL statements like CREATE,ALTER,DROP,TRUNCATE etc.
Use Alias
If an alias is not present, the engine must resolve which tables own the specified columns. A short alias is parsed more quickly than a long table name or alias. If possible, reduce the alias to a single letter
--Wrong Statement
SELECT PromotionId,P.VersionedPromotionId,Name,PIE.InvestmentTypeIdfromPromotion P
Inner join PromotionInvestmentPIE onPIE.VersionedPromotionId=P.VersionedPromotionId
where P.Name='Blah'
--Correct Statement
SELECT P.PromotionId,P.VersionedPromotionId,P.Name,PIE.InvestmentTypeIdfromPromotion P
Inner join PromotionInvestmentPIE onPIE.VersionedPromotionId=P.VersionedPromotionId
where P.Name='Blah'
Don't use UPDATE instead of CASE
Take this scenario, for instance: You're inserting data into a temp table and need it to display a certain value if another value exists. Maybe you're pulling from the Customer table and you want anyone with more than $100,000 in orders to be labeled as "Preferred." Thus, you insert the data into the table and run an UPDATE statement to set the CustomerRankcolumn to "Preferred" for anyone who has more than $100,000 in orders. The problem is that the UPDATE statement is logged, which means it has to write twice for every single write to the table. The way around this, of course, is to use an inline CASE statement in the SQL query itself. This tests every row for the order amount condition and sets the "Preferred" label before it's written to the table.
Avoid Functions on RHS
Dont use this
select *
from Promotion
where YEAR(StartDate)=2015
and MONTH(StartDate)=6
Use this
Select *
From Promotion
Where StartDatebetween'6/1/2015'
and'6/30/2015'
Specify optimizer hints in SELECT
most cases the query optimizer will pick the appropriate index for a particular table based on statistics, sometimes it is better to specify the index name in your SELECT query.
Do not use this unless you know what you are doing.
SELECT *
FROM Promotion
WITH ( Index(IdxPromotionId))
WHERE Name ='blah'
and Setupid=1099
Hope these tips will help you prevent and solve the timeout exception you face. If you want to add any please mention in the comments.
