Simple Optimizations for Web Applications (asp.net, sqlserver)

jldajo — Fri, 06 May 2011 17:33:08 +0000

Hi! This is my first technical post in my personal blog. Hope you find this useful, and this is also for my personal reference.

1. Call stored procedures as dbo.sprocName. This increases the chance of reusing execution plan and also reduces confusion on which stored procedure you want to run. Also, at the very least, reference tables as dbo.tblName.

SELECT * FROM dbo.tblCustomers
sp_executesql(dbo.uspDebug)
Dim cmd as New SqlCommand(“dbo.usp_tblCustomers_Insert”)

2. Add ‘SET NO COUNT ON’ at the beginning of each stored procedure.

3. Create a primary key on each table you create. This will automatically set a clustered index in your table. Index seeks are faster than table scans.

CREATE TABLE tblOrders
(orderId UNIQUEIDENTIFIER NOT NULL DEFAULT newid()
, orderNo INT IDENTITY
, customerId UNIQUEIDENTIFIER NOT NULL DEFAULT ’00000000-0000-0000-0000-000000000000′
, orderStatus NVARCHAR(100) NOT NULL DEFAULT ”
, createdDate SMALLDATETIME NOT NULL DEFAULT getdate()
, createdBy INT NOT NULL DEFAULT 0
, modifiedDate SMALLDATETIME NOT NULL DEFAULT getdate()
, modifiedBy INT NOT NULL DEFAULT 0
, deletedDate SMALLDATETIME
, deletedBy INT NOT NULL DEFAULT 0
, deleteStatus INT NOT NULL DEFAULT 0
, PRIMARY KEY(orderId)
)

or when table already exists but has no primary key

ALTER TABLE tblOrders ADD PRIMARY KEY(order_id)

4. Create indexes on foreign keys and columns that are most likely will get filtered, joined, sorted and grouped by. (Indexes needs to be unique within the table, and not necessarily within the whole database)

CREATE INDEX IDX_orderNo ON tblOrders(orderNo)
CREATE INDEX IDX_customerId ON tblOrders(customerId)

5. Examine your WHERE clause. Add parenthesis when combining AND and OR filters. For combinations of AND statements, they are evaluated from left to right, so follow these:

a. Least likely true first (eliminate as soon as possible)
b. Least complicated first (reduce cpu cycles)
c. Avoid functions on left side
instead of …WHERE getGerman(word) = ‘gut’
use …WHERE word = getEnglish(‘gut’)

6. Only return the rows and columns that you need.

7. Use inline and block comments in your SQL code. One is to enhance productivity. Two is to remove unnecessary processes in your stored procedures, by commenting them out. Having comments doesn’t really affect performance of stored procedure.

8. Reduce number of round trips to the database server

a. Return multiple result sets
b. For header-detail tables, build detail table first, then aggregate for header table, all in one stored procedure.

9. Profile your stored procedures
a. SET STATISTICS IO ON
b. SET STATISTICS TIME ON
c. Examine actual execution plan
d. Use SQL Profiler, then identify long running stored procedures
e. Use SQL Profiler, then identify queries called very often

10. Avoid cursors. You may use CASE, multiple queries, simple joins or table variables instead.
Instead of this:

ALTER PROC sp_OrderItems_Cursored
@bom_id UNIQUEIDENTIFIER
AS
SET NOCOUNT ON

DECLARE @order_details_id UNIQUEIDENTIFIER
, @order_id UNIQUEIDENTIFIER
, @SizeRangeID UNIQUEIDENTIFIER

DECLARE curOrderItems CURSOR FOR
SELECT order_details_id, order_id, SizeRangeID
FROM dbo.tblOrdersDetails WHERE bom_id = @bom_id
OPEN curOrderItems

FETCH curOrderItems INTO
@order_details_id, @order_id, @SizeRangeId

WHILE @@Fetch_Status = 0
BEGIN

SELECT @order_details_id, @order_id, @SizeRangeId

FETCH curOrderItems INTO
@order_details_id, @order_id, @SizeRangeId

END
CLOSE curOrderItems
DEALLOCATE curOrderItems

GO — END SP

Do this:

ALTER PROC sp_OrderItems_Tabled
@bom_id UNIQUEIDENTIFIER
AS

SET NOCOUNT ON

CREATE TABLE dbo.#orderItems(
idx INT IDENTITY
, order_details_id UNIQUEIDENTIFIER
, order_id UNIQUEIDENTIFIER
, SizeRangeID UNIQUEIDENTIFIER
, PRIMARY KEY(idx)
)

INSERT INTO dbo.#orderItems(order_details_id, order_id, SizeRangeID)
SELECT order_details_id, order_id, SizeRangeID
FROM dbo.tblOrdersDetails WHERE bom_id = @bom_id

DECLARE @idx INT, @total INT

SELECT @idx = 1, @total = COUNT(*) FROM dbo.#orderItems

WHILE @idx
BEGIN

DECLARE @order_details_id UNIQUEIDENTIFIER,
@order_id UNIQUEIDENTIFIER,
@SizeRangeID UNIQUEIDENTIFIER

SELECT
@order_details_id = order_details_id
, @order_id = order_id
, @SizeRangeID = SizeRangeID
FROM dbo.#orderItems
WHERE idx = @idx

SELECT @order_details_id
, @order_id
, @SizeRangeId

SET @idx = @idx + 1

END

DROP TABLE dbo.#orderItems

GO — END SP

* This is an example of temporary table. It is still best to use SET-BASED approach (e.g. simple joins), rather than procedural approach (e.g. functions, sequential table access).

11. In Asp.Net, use USING in sql connections to ensure that SqlConnections are closed. Open as late as possible and close as early as possible.

Using con as New SqlConnection(strCon)
…
con.Open()
…
cmd.ExecuteNonQuery()
con.Dispose()
…
End Using

12. Initialize SqlCommands using stored procedure names only.
Instead of:

Dim cmd as New SqlCommand(“dbo.sp_tblDebug_Insert @msg = ‘” & str & “’”)

Do this:

Dim cmd as New SqlCommand(“dbo.sp_tblDebug_Insert”, con)

cmd.CommandType = CommandType.StoredProcedure

SqlCommandBuilder.DeriveParameters(cmd)

cmd.Parameters(“@msg”).Value = str

13. Avoid unnecessary round trips to the database

a. Don’t rebind if not needed. Use IsPostback and viewstate.

b. Stored procedure may return multiple result sets

14. Use var += 1, instead of var = var + 1 to avoid evaluating val twice.

15. For paging and sorting datagrids with large/complex data, it is better to have logic for paging in the stored procedure (i.e. stored procedure accepts page). Improves performance both in ASP and in SQL Server.

16. Use Server.Transfer instead of Response.Redirect.

17. Minimize calls to Databinder.Eval

For ItemDataBounds having datatables as datasource, use this instead:
lblBomRef.Text = DirectCast(e.Row.DataItem, DataRowView)(“bom_ref”).ToString()

18. Minimize the use of Server controls. Only use server controls when they are required, otherwise, use standard HTML controls for faster rendering. e.g. use rather than

19. Disable viewstate for pages

a. that has minimal input processing (e.g. HTML Reports, Pages with DataGrids)
b. that does not postback
c. that rebuilds the server controls anyway whenever page is loaded.

Add this attribute: <% Page EnableViewState=”False” %>

Note that you may also disable viewstates for certain controls only. Or you may also try disabling viewstate for the page and testing your page. If it doesn’t work, then enable.

20. Disable session state for aspx that doesn’t use sessions
If page just gets values from session variables, but does not modify it, set it to readonly.

21. Optimize string usage:

a. Use the Equals method rather than the = operation
Boolean blEqual = strExample.Equals(strInput)
b. Use String.Empty rather than “”
c. Use String.Length to check an empty string
d. Do not create string instances inside of loop
e. Use StringBuilder for concatenating more than 4 strings

StringBuilder Sb = new StringBuilder()
Sb.Append(“
”)
Sb.Append(“
This is a message to ”)
Sb.Append(strPerson)
…
strMessage = Sb.ToString()
…

22. Keep

Ang Pinaka-Walang Kwentang Blog

Simple Optimizations for Web Applications (asp.net, sqlserver)