2. Optimizing Microsoft SQL Server 2008 Applications Using Table Valued Parameters, XML, and MERGE
Michael Rys
Principal Program Manager Lead
Microsoft Corporation
Session Code: DAT 406

3. Agenda Passing a set of data to SQL Server
Adding MERGE to the equation

4. Passing a set of data to SQL Server
N rows = N executed statements
N rows = 1 executed statement

5. Passing a set of data to SQL Server
N rows = N executed statements
One client server roundtrip per execution
All executions in one batch

6. Passing a set of data to SQL Server
N rows = 1 executed statement
Pass the data as a delimited list
Pass the data as XML
Pass the data as Table Valued Parameter
Other options
Managed bulk copy to a table
Pass data as separate arguments (current limit is 2100)

7. Examples
In the examples we will be passing a set of items to the database for storage
Example - “Store the following 1000 items”
Examples will use
Stored Procedures
C# & ADO.NET

8. Pass the data as a delimited list
// C#
cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText =
…|…|…
…|…|…"); cmd.Execute…;
-- What happens on the server?
EXEC = '…|…|…
…|…|…';

9. Pass the data as a delimited list
To get the best performance we need to use a SQLCLR Table Valued Function
Pros
Performance is good
No exposure to SQL Injection
Cons
Requires SQLCLR to be enabled on the instance
The set of data is not strongly typed
Cumbersome implementation
Can be simplified by created one TVF per “list type”

10. Pass the data as XML // C#
cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "Test.spXML"; doc.OuterXml); cmd.Execute…;
-- What happens on the server?:
EXEC = N'<Orders><Order…

11. Pass the data as XML Pros Cons
Strongly typed (if you use an XML Schema Collection)
Performance is OK
No exposure to SQL Injection
A very good option if your data is already XML!
Great flexibility, remember XML allows for hierarchies
Cons
Performance is good but not the best
Requires knowledge about XML
Less cumbersome than the delimited list but still somewhat cumbersome

12. Pass the data as a Table Valued Parameter
// C#
cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "Test.spTVP"; var p = SqlDbType.Structured); p.TypeName = "Test.OrderTableType"; p.Value = dataTable;
cmd.Execute…;
-- What happens on the server?:
Test.OrderTableType; …
EXEC

13. Pass the data as Table Valued Parameter
Pros
Strongly typed
No exposure to SQL Injection
Performance is great!
Very easy to use, both on client and server side
Cons
Less flexible than XML, may require you to pass multiple TVPs where one XML parameter would have been enough
Allows for streaming, but only to the server

14. Table Valued Parameters
Similar to Table Valued Variables
Live in tempdb
No limit on numbers of rows
Parameter sniffing will get table statistics!
Limitations
No sparse columns
No indexes (except through constraints)

15. Pass the data as a Table Valued Parameter  Streaming
// C#
class MyStreamingTvp : IEnumerable<SqlDataRecord> { … }
… cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "Test.spTVP"; var p = SqlDbType.Structured); p.TypeName = "Test.OrderTableType"; p.Value = new MyStreamingTvp(…);
cmd.Execute…; -- What happens on the server?:
Test.OrderTableType; …
EXEC

16. Pass the data as a Table Valued Parameter  Streaming
Pros
No need for staging the data in memory on the client side
Cons
Doesn’t stream all the way, stages the data on the server side
Requires a type to handle the streaming

17. A few more words on Streaming
If you stream, how “far” do you stream?
N rows = N client server round trips & N proc. executions
Streams “all” the way to the destination table
Streaming TVP
Streams from client to just before the procedure begins execution, i.e. stages the data on the server side
The rest
Stages the data both on the client and server side
Any solution can implement streaming “manually”

18. What happens? And what about performance?
Initial parsing of the data on the Server
Querying the data
Insert the data into a table

19. 1. Initial parsing on the Server

20. 1. Initial parsing on the Server

21. 2. Querying the data

22. 2. Querying the data

23. 3. Insert the arguments into a table

24. 3. Insert the data into a table

25. Agenda Passing a set of data to SQL Server
Adding MERGE to the equation

26. Adding MERGE to the equation
Also referred to as UPSERT
Allows for inserting, updating and deleting data in one statement
It is part of ANSI
…with one addition!

27. Adding MERGE to the equation
Events
MATCHED
NOT MATCHED
NOT MATCHED BY SOURCE
Type of event
$action

28. Adding MERGE to the equation
MERGE Test.Orders AS o
AS v
ON v.OrderId = o.OrderId
WHEN MATCHED THEN
UPDATE SET
CustomerId = v.CustomerId
,OrderDate = v.OrderDate
,DueDate = v.DueDate
WHEN NOT MATCHED BY SOURCE THEN
DELETE
WHEN NOT MATCHED THEN
INSERT (OrderId, CustomerId, OrderDate)
VALUES(v.OrderId, v.CustomerId, v.OrderDate);

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