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

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

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

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

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)

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

Pass the data as a delimited list // C# cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "Test.spDelimitedString"; cmd.Parameters.AddWithValue("@Values", @"…|…|… …|…|… …|…|…"); cmd.Execute…; -- What happens on the server? EXEC Test.spDelimitedString @Values = '…|…|… …|…|…';

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”

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

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

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

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

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)

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

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

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”

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

1. Initial parsing on the Server

1. Initial parsing on the Server

2. Querying the data

2. Querying the data

3. Insert the arguments into a table

3. Insert the data into a table

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

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!

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

Adding MERGE to the equation MERGE Test.Orders AS o USING @Values 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);

question & answer Meet me in the Ask-the-Experts pavilion! http://connect.microsoft.com/sqlserver/feedback

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